Genetic loci associated with Fusarium solani tolerance in soybean

ABSTRACT

The invention relates to methods and compositions for identifying soybean plants that are tolerant, have improved tolerance or are susceptible to  Fusarium solani  infection (the causative agent of sudden death syndrome or SDS). The methods use molecular genetic markers to identify, select and/or construct disease-tolerant plants or identify and counterselect disease-susceptible plants. Soybean plants that display tolerance or improved tolerance to  Fusarium solani  infection that are generated by the methods of the invention are also a feature of the invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of U.S. ProvisionalPatent Application Ser. No. 60/599,777, filed on Aug. 6, 2004, and U.S.Provisional Patent Application Ser. No. 60/599,705, filed on Aug. 6,2004, the specifications of which are hereby incorporated by referencein their entirety.

FIELD OF THE INVENTION

The invention relates to compositions and methods for identifyingsoybean plants that are tolerant, have improved tolerance or aresusceptible to Fusarium solani infection (the causative agent of suddendeath syndrome), where the methods use molecular genetic markers toidentify, select and/or construct disease-tolerant plants. The inventionalso relates to soybean plants that display tolerance or improvedtolerance to Fusarium solani infection that are generated by the methodsof the invention.

BACKGROUND OF THE INVENTION

Soybean, a legume, has become the world's primary source of seed oil andseed protein. In addition, its utilization is being expanded to theindustrial, manufacturing and pharmaceutical sectors. Soybeanproductivity is a vital agricultural and economic consideration.Unfortunately, soybean is host to one of the widest ranges of infectiouspathogens of all crops. More than a hundred different pathogens areknown to affect soybean plants, some of which pose significant economicthreats. Improving soybean disease tolerance to these many pathogens iscrucial to preventing yield losses.

Fusarium solani f.sp Glycines and Sudden Death Syndrome

One of the most destructive fungal diseases of soybean [Glycine max (L.)Merr.] is sudden death syndrome (SDS). See, Wrather et al. (1996)“Soybean Disease loss estimates for the top ten producing countriesduring 1994,” Plant Dis. 81:107-110, and Wrather et al. (1995) “Soybeandisease loss estimates for southern United States, 1974 to 1994,” PlantDis. 79:1076-1079. This disease is caused by a pathogenic fungalinfection of Fusarium solani (e.g., Fusarium solani f.sp glycines and/orFusarium solani f.sp phaseoli, two closely related, or possibly congenicFusarium solani species). This pathogen enters the roots and crowns ofthe plant and grows through the plant's vascular system, eventuallycausing foliar scorch, sudden wilting and death of the plant during thegrowing season. See, Gibson (1994) “Soybean varietal response to suddendeath syndrome,” pp 20-40 in D. Wilkinson (ed.) Proc. Twenty-FourthSoybean Seed Res. Conf. Chicago Ill. for Am Seed Trade Assoc.,Washington D.C.; and Rupe et al. (1991) Plant Dis. 75:47-50).

A common method of protecting soybean plants from SDS uses the selectionof SDS tolerant plants, such as those found in the cultivars “Forrest”(Hartwig and Epps (1973) “Registration of Forrest Soybean” Crop Sci.13:287) “Pyramid” (Myers et. (1988) Crop Sci 28:375-376) and “Essex.”During marker assisted selection (MAS), plant breeders select forspecific tolerance loci in an attempt to produce plants that aretolerant to infection, or that limit the extent of the infection. Forexample, a Forrest allele of the genomic region on linkage group G andan Essex allele of a portion of the genomic region on linkage group C2are each associated with decreased disease index measurements for SDS(Nijiti et al. (1998) “Resistance to Soybean Sudden Death Syndrome andRoot Colonization by Fusarium solani f.sp. glycine in Near IsogenicLines.” Crop Sci. 38:472-477; Chang et al. (1996) “two additional lociunderlying durable field resistance to sudden death syndrome (SDS)” CropSci 36:1684-1688. Linkage groups A2, B and G have been identified asunderlying resistance traits in Pyramid. Field resistance to SDS isincomplete, with, for example, Forrest (but not Essex) being resistantto colonization of plant taproot by F. solani, while Essex is moreresistant to development of foliar SDS symptoms. See also, Nijiti et al.(1997) “Rate reducing resistance to Fusarium solani f.sp phaseoliunderlies field resistance to soybean sudden death syndrome (SDS) CropSci. 37:132-138 and Gibson et al. (1994) supra.

A common method of protecting soybean plants from Fusarium solani SDSutilizes the selection of specific resistance genes. Plant breedersmanipulate specific resistance genes in an attempt to produce plantsthat are resistant to infection, or limit the extent of the infection.Unfortunately, as breeders evolve increasingly resistant strains, thehost range of the pathogen similarly evolves to adapt to the changinggenetic constitution of the host. Thus, resistant soybean strainsproduced by plant breeders are effective only for a finite period andeventually fail.

An alternative approach is to identify plants that show tolerance to aparticular pathogen. Tolerance can be described as the relative abilityof a plant to survive infection without showing severe symptoms such asdeath, stunting, loss of vigor or yield loss. Tolerance includes anymechanism other than whole-plant immunity or resistance that reduces theexpression of symptoms indicative of infection. Infected plants thatexhibit tolerance will yield nearly as well as uninfected plants andalso prevent the evolution of host-adapted pathogenic Fusarium solaniraces capable of reducing soybean yield in previously resistant plants.

The development of molecular genetic markers has facilitated mapping andselection of agriculturally important traits in soybean. Markers tightlylinked to disease tolerance genes are an asset in the rapididentification of tolerant soybean lines on the basis of genotype by theuse of marker assisted selection (MAS). Introgressing disease tolerancegenes into a desired cultivar would also be facilitated by usingsuitable DNA markers.

Molecular Markers and Marker Assisted Selection

A genetic map is a graphical representation of a genome (or a portion ofa genome such as a single chromosome) where the distances betweenlandmarks on the chromosome are measured by the recombinationfrequencies between the landmarks. A genetic landmark can be any of avariety of known polymorphic markers, for example but not limited to,molecular markers such as SSR markers, RFLP markers, or SNP markers.Furthermore, SSR markers can be derived from genomic or expressednucleic acids (e.g., ESTs). The nature of these physical landmarks andthe methods used to detect them vary, but all of these markers arephysically distinguishable from each other (as well as from theplurality of alleles of any one particular marker) on the basis ofpolynucleotide length and/or sequence.

Although specific DNA sequences which encode proteins are generallywell-conserved across a species, other regions of DNA (typicallynon-coding) tend to accumulate polymorphism, and therefore, can bevariable between individuals of the same species. Such regions providethe basis for numerous molecular genetic markers. In general, anydifferentially inherited polymorphic trait (including nucleic acidpolymorphism) that segregates among progeny is a potential marker. Thegenomic variability can be of any origin, for example, insertions,deletions, duplications, repetitive elements, point mutations,recombination events, or the presence and sequence of transposableelements. A large number of soybean molecular markers are known in theart, and are published or available from various sources, such as theSOYBASE internet resource. Similarly, numerous methods for detectingmolecular markers are also well-established.

The primary motivation for developing molecular marker technologies fromthe point of view of plant breeders has been the possibility to increasebreeding efficiency through marker assisted selection (MAS). A molecularmarker allele that demonstrates linkage disequilibrium with a desiredphenotypic trait (e.g., a quantitative trait locus, or QTL, such asresistance to a particular disease) provides a useful tool for theselection of a desired trait in a plant population. The key componentsto the implementation of this approach are: (i) the creation of a densegenetic map of molecular markers, (ii) the detection of QTL based onstatistical associations between marker and phenotypic variability,(iii) the definition of a set of desirable marker alleles based on theresults of the QTL analysis, and (iv) the use and/or extrapolation ofthis information to the current set of breeding germplasm to enablemarker-based selection decisions to be made.

The availability of integrated linkage maps of the soybean genomecontaining increasing densities of public soybean markers hasfacilitated soybean genetic mapping and MAS. See, e.g., Cregan et al.(1999) “An Integrated Genetic Linkage Map of the Soybean Genome” CropSci. 39:1464-1490; Song et al., “A New Integrated Genetic Linkage Map ofthe Soybean,” Theor. Appl. Genet., 109:122-128 (2004); Diwan and Cregan(1997) “Automated sizing of fluorescent-labeled simple sequence repeat(SSR) markers to assay genetic variation in Soybean,” Theor. Appl.Genet., 95:220-225; the Soybase resources on the world wide web atsoybase.org, including the Shoemaker Lab Home Page and other resourcesthat can be accessed through Soybase; and see the Soybean Genomics andImprovements Laboratory (SGIL) on the world wide web, and see especiallythe Cregan Lab web site.

Two types of markers are frequently used in marker assisted selectionprotocols, namely simple sequence repeat (SSR, also known asmicrosatellite) markers, and single nucleotide polymorphism (SNP)markers. The term SSR refers generally to any type of molecularheterogeneity that results in length variability, and most typically isa short (up to several hundred base pairs) segment of DNA that consistsof multiple tandem repeats of a two or three base-pair sequence. Theserepeated sequences result in highly polymorphic DNA regions of variablelength due to poor replication fidelity, e.g., caused by polymeraseslippage. SSRs appear to be randomly dispersed through the genome andare generally flanked by conserved regions. SSR markers can also bederived from RNA sequences (in the form of a cDNA, a partial cDNA or anEST) as well as genomic material.

The characteristics of SSR heterogeneity make them well suited for useas molecular genetic markers; namely, SSR genomic variability isinherited, is multiallelic, codominant and is reproducibly detectable.The proliferation of increasingly sophisticated amplification-baseddetection techniques (e.g., PCR-based) provides a variety of sensitivemethods for the detection of nucleotide sequence heterogeneity. Primers(or other types of probes) are designed to hybridize to conservedregions that flank the SSR domain, resulting in the amplification of thevariable SSR region. The different sized amplicons generated from an SSRregion have characteristic and reproducible sizes. The different sizedSSR amplicons observed from two homologous chromosomes in an individual,or from different individuals in the plant population are generallytermed “marker alleles.” As long as there exists at least two SSRalleles that produce PCR products with at least two different sizes, theSSRs can be employed as a marker.

Soybean markers that rely on single nucleotide polymorphisms (SNPs) arealso well known in the art. Various techniques have been developed forthe detection of SNPs, including allele specific hybridization (ASH;see, e.g., Coryell et al., (1999) “Allele specific hybridization markersfor soybean,” Theor. Appl. Genet., 98:690-696). Additional types ofmolecular markers are also widely used, including but not limited toexpressed sequence tags (ESTs) and SSR markers derived from ESTsequences, restriction fragment length polymorphism (RFLP), amplifiedfragment length polymorphism (AFLP), randomly amplified polymorphic DNA(RAPD) and isozyme markers. A wide range of protocols are known to oneof skill in the art for detecting this variability, and these protocolsare frequently specific for the type of polymorphism they are designedto detect. For example, PCR amplification, single-strand conformationpolymorphisms (SSCP) and self-sustained sequence replication (3SR; seeChan and Fox, “NASBA and other transcription-based amplification methodsfor research and diagnostic microbiology,” Reviews in MedicalMicrobiology 10:185-196 [1999]).

Linkage of one molecular marker to another molecular marker is measuredas a recombination frequency. In general, the closer two loci (e.g., twoSSR markers) are on the genetic map, the closer they lie to each otheron the physical map. A relative genetic distance (determined by crossingover frequencies, measured in centimorgans; cM) is generallyproportional to the physical distance (measured in base pairs, e.g.,kilobase pairs [kb] or megabasepairs [Mbp]) that two linked loci areseparated from each other on a chromosome. A lack of preciseproportionality between cM and physical distance can result fromvariation in recombination frequencies for different chromosomalregions, e.g., some chromosomal regions are recombinational “hot spots,”while others regions do not show any recombination, or only demonstraterare recombination events. In general, the closer one marker is toanother marker, whether measured in terms of recombination or physicaldistance, the more strongly they are linked. In some aspects, the closera molecular marker is to a gene that encodes a polypeptide that impartsa particular phenotype (disease tolerance), whether measured in terms ofrecombination or physical distance, the better that marker serves to tagthe desired phenotypic trait.

Genetic mapping variability can also be observed between differentpopulations of the same crop species, including soybean. In spite ofthis variability in the genetic map that may occur between populations,genetic map and marker information derived from one population generallyremains useful across multiple populations in identification of plantswith desired traits, counter-selection of plants with undesirable traitsand in guiding MAS.

QTL Mapping

It is the goal of the plant breeder to select plants and enrich theplant population for individuals that have desired traits, for example,pathogen tolerance, leading ultimately to increased agriculturalproductivity. It has been recognized for quite some time that specificchromosomal loci (or intervals) can be mapped in an organism's genomethat correlate with particular quantitative phenotypes. Such loci aretermed quantitative trait loci, or QTL. The plant breeder canadvantageously use molecular markers to identify desired individuals byidentifying marker alleles that show a statistically significantprobability of co-segregation with a desired phenotype (e.g., pathogenicinfection tolerance), manifested as linkage disequilibrium. Byidentifying a molecular marker or clusters of molecular markers thatco-segregate with a quantitative trait, the breeder is thus identifyinga QTL. By identifying and selecting a marker allele (or desired allelesfrom multiple markers) that associates with the desired phenotype, theplant breeder is able to rapidly select a desired phenotype by selectingfor the proper molecular marker allele (a process called marker-assistedselection, or MAS). The more molecular markers that are placed on thegenetic map, the more potentially useful that map becomes for conductingMAS.

Multiple experimental paradigms have been developed to identify andanalyze QTL (see, e.g., Jansen (1996) Trends Plant Sci 1:89). Themajority of published reports on QTL mapping in crop species have beenbased on the use of the bi-parental cross (Lynch and Walsh (1997)Genetics and Analysis of Quantitative Traits, Sinauer Associates,Sunderland). Typically, these paradigms involve crossing one or moreparental pairs, which can be, for example, a single pair derived fromtwo inbred strains, or multiple related or unrelated parents ofdifferent inbred strains or lines, which each exhibit differentcharacteristics relative to the phenotypic trait of interest. Typically,this experimental protocol involves deriving 100 to 300 segregatingprogeny from a single cross of two divergent inbred lines (e.g.,selected to maximize phenotypic and molecular marker differences betweenthe lines). The parents and segregating progeny are genotyped formultiple marker loci and evaluated for one to several quantitativetraits (e.g., disease resistance). QTL are then identified assignificant statistical associations between genotypic values andphenotypic variability among the segregating progeny. The strength ofthis experimental protocol comes from the utilization of the inbredcross, because the resulting F1 parents all have the same linkage phase.Thus, after selfing of the F1 plants, all segregating progeny (F2) areinformative and linkage disequilibrium is maximized, the linkage phaseis known, there are only two QTL alleles, and, except for backcrossprogeny, the frequency of each QTL allele is 0.5.

Numerous statistical methods for determining whether markers aregenetically linked to a QTL (or to another marker) are known to those ofskill in the art and include, e.g., standard linear models, such asANOVA or regression mapping (Haley and Knott (1992) Heredity 69:315),maximum likelihood methods such as expectation-maximization algorithms,(e.g., Lander and Botstein (1989) “Mapping Mendelian factors underlyingquantitative traits using RFLP linkage maps,” Genetics 121:185-199;Jansen (1992) “A general mixture model for mapping quantitative traitloci by using molecular markers,” Theor. Appl. Genet., 85:252-260;Jansen (1993) “Maximum likelihood in a generalized linear finite mixturemodel by using the EM algorithm,” Biometrics 49:227-231; Jansen (1994)“Mapping of quantitative trait loci by using genetic markers: anoverview of biometrical models,” In J. W. van Ooijen and J. Jansen(eds.), Biometrics in Plant breeding: applications of molecular markers,pp. 116-124, CPRO-DLO Metherlands; Jansen (1996) “A general Monte Carlomethod for mapping multiple quantitative trait loci,” Genetics142:305-311; and Jansen and Stam (1994) “High Resolution of quantitativetrait into multiple loci via interval mapping,” Genetics 136:1447-1455).Exemplary statistical methods include single point marker analysis,interval mapping (Lander and Botstein (1989) Genetics 121:185),composite interval mapping, penalized regression analysis, complexpedigree analysis, MCMC analysis, MQM analysis (Jansen (1994) Genetics138:871), HAPLO-IM+ analysis, HAPLO-MQM analysis, and HAPLO-MQM+analysis, Bayesian MCMC, ridge regression, identity-by-descent analysis,Haseman-Elston regression, any of which are suitable in the context ofthe present invention. In addition, additional details regardingalternative statistical methods applicable to complex breedingpopulations which can be used to identify and localize QTLs aredescribed in: U.S. Ser. No. 09/216,089 by Beavis et al. “QTL MAPPING INPLANT BREEDING POPULATIONS” and PCT/US00/34971 by Jansen et al. “MQMMAPPING USING HAPLOTYPED PUTATIVE QTLS ALLELES: A SIMPLE APPROACH FORMAPPING QTLS IN PLANT BREEDING POPULATIONS.” Any of these approaches arecomputationally intensive and are usually performed with the assistanceof a computer based system and specialized software. Appropriatestatistical packages are available from a variety of public andcommercial sources, and are known to those of skill in the art.

There is a need in the art for improved soybean strains that aretolerant to Fusarium solani infections, such as Fusarium solani f.spglycines infections. There is a need in the art for methods thatidentify soybean plants or populations (germplasm) that displaytolerance to Fusarium solani infection. What is needed in the art is toidentify molecular genetic markers that are linked to Fusarium solanitolerance loci (e.g., tolerance QTL) in order to facilitate MAS, andalso to facilitate gene discovery and cloning of gene alleles thatimpart Fusarium solani infection tolerance. Such markers can be used toselect individual plants and plant populations that show favorablemarker alleles in soybean populations and then employed to select thetolerant phenotype, or alternatively, be used to counterselect plants orplant populations that show a Fusarium solani infection susceptibilityphenotype. The present invention provides these and other advantages.

SUMMARY OF THE INVENTION

Compositions and methods for identifying soybean plants or germplasmwith tolerance to Fusarium solani infection are provided. Methods ofmaking soybean plants or germplasm that are tolerant to Fusarium solaniinfection, e.g., through introgression of desired tolerance markeralleles and/or by transgenic production methods, as well as plants andgermplasm made by these methods, are also provided. Systems and kits forselecting tolerant plants and germplasm are also a feature of theinvention.

Fusarium solani is a major disease of soybean, causing severe losses insoybean viability and overall yield. Fusarium solani resistant soybeancultivars have been produced in an attempt to reduce these losses.However, the strong selective pressures that resistant soybean impose onFusarium solani cause relatively rapid loss of the resistance phenotype.In contrast, tolerance to Fusarium solani infection, in which the plantsurvives and produces high yields, despite a productive Fusarium solaniinfection, is an alternate strategy to combat losses due to Fusariumsolani infection. Pathogen tolerance provides advantages over pathogenresistance. Selection for pathogen tolerance in the plant is less likelyto result in the evolution of destructive races of Fusarium solani thatcombat and overcome the tolerance traits, leading to a host/pathogenrelationship that more resembles commensalism as opposed to parasitism.

The identification and selection of soybean plants that show toleranceto Fusarium solani sudden death syndrome using MAS can provide aneffective and environmentally friendly approach to overcoming lossescaused by this disease. The present invention provides a number ofsoybean marker loci and QTL chromosome intervals that demonstratestatistically significant co-segregation with Fusarium solani tolerance.Detection of these QTL markers or additional loci linked to the QTLmarkers can be used in marker-assisted soybean breeding programs toproduce tolerant plants, or plants with improved tolerance.

In some aspects, the invention provides methods for identifying a firstsoybean plant or germplasm (e.g., a line or variety) that has tolerance,improved tolerance or susceptibility to Fusarium solani infection. Inthe methods, at least one allele of one or more marker locus (e.g., aplurality of marker loci) that is associated with the tolerance,improved tolerance or susceptibility are detected in the first soybeanplant or germplasm. The marker loci can be selected from the lociprovided in FIG. 1, including: SATT300, SATT591, SATT155, SATT266,SATT282, SATT412, SATT506, SATT355, SATT452, S60602-TB, SATT142,SATT181, SATT448, S60375-TB, SATT513, SATT549, SATT660, SATT339 andSATT255, as well as any other marker that is closley linked to these QTLmarkers (e.g., within about 10 cM of these loci). The invention alsoprovides chromosomal QTL intervals that correlate with Fusarium solaniinfection tolerance. These intervals are located on linkage groups A1,D1b and N. Any marker located within these intervals also finds use as amarker for Fusarium solani infection tolerance. These intervals include:

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N).

A plurality of maker loci can be selected in the same plant. Which QTLmarkers are selected in combination is not particularly limited. The QTLmarkers used in combinations can be any of the makers listed in FIG. 1,any other marker that is closely linked to the markers in FIG. 1 (e.g.,the closely linked markers as determined from FIG. 4 and FIG. 5, ordetermined from the SOYBASE resource), or any marker within the QTLintervals described herein.

The markers that are linked to the QTL markers of the invention (e.g.,those markers provided in FIG. 1) are closely linked, for example,within about 10 cM from the QTL markers. In desirable embodiments, thelinked locus displays a genetic recombination distance of 9centiMorgans, 8, 7, 6, 5, 4, 3, 2, 1, 0.75, 0.5 or 0.25, or less fromthe QTL marker. In some embodiments, the closely linked locus isselected from the list of marker loci determined from FIG. 4 or FIG. 5.

In some embodiments, preferred QTL markers are selected from SATT591,SATT155, SATT266, SATT412, SATT506, SATT355, SATT452, SATT549, SATT660,SATT339 and SATT255.

In some embodiments, the germplasm is a soybean line or variety. In someaspects, the tolerance or improved tolerance is a non-race specifictolerance or a non-race specific improved tolerance. In some aspects,the tolerance, improved tolerance or susceptibility of a soybean plantto Fusarium solani infection can be quantitated using any suitablemeans, for example, by assaying soybean infection in a field whereFusarium solani infection occurs naturally. In some aspects, theFusarium solani is Fusarium solani f. sp. glycines. In other aspects,the tolerance or improved tolerance is a non-race specific tolerance ora non-race specific improved tolerance.

Any of a variety of techniques can be used to identify a marker allele.It is not intended that the method of allele detection be limited in anyway. Methods for allele detection typically include molecularidentification methods such as amplification and detection of the markeramplicon. For example, an allelic form of a polymorphic simple sequencerepeat (SSR), or of a single nucleotide polymorphism (SNP) can bedetected, e.g., by an amplification based technology. In these and otheramplification based detection methods, the marker locus or a portion ofthe marker locus is amplified (e.g., via PCR, LCR or transcription usinga nucleic acid isolated from a soybean plant of interest as a template)and the resulting amplified marker amplicon is detected. In one exampleof such an approach, an amplification primer or amplification primerpair is admixed with genomic nucleic acid isolated from the firstsoybean plant or germplasm, wherein the primer or primer pair iscomplementary or partially complementary to at least a portion of themarker locus, and is capable of initiating DNA polymerization by a DNApolymerase using the soybean genomic nucleic acid as a template. Theprimer or primer pair (e.g., a primer pair provided in FIG. 2) isextended in a DNA polymerization reaction having a DNA polymerase and atemplate genomic nucleic acid to generate at least one amplicon. In anycase, data representing the detected allele(s) can be transmitted (e.g.,electronically or via infrared, wireless or optical transmission) to acomputer or computer readable medium for analysis or storage. In someembodiments, plant RNA is the template for the amplification reaction.In other embodiments, plant genomic DNA is the template for theamplification reaction. In some embodiments, the QTL marker is a SNPtype marker, and the detected allele is a SNP allele, and the method ofdetection is allele specific hybridization (ASH).

In some embodiments, the allele that is detected is a favorable allelethat positively correlates with tolerance or improved tolerance. In thecase where more than one marker is selected, an allele is selected foreach of the markers; thus, two or more alleles are selected. In someembodiments, it can be the case that a marker locus will have more thanone advantageous allele, and in that case, either allele can beselected.

It will be appreciated that the ability to identify QTL marker loci thatcorrelate with tolerance, improved tolerance or susceptibility of asoybean plant to Fusarium solani infection provides a method forselecting plants that have favorable marker loci as well. That is, anyplant that is identified as comprising a desired marker locus (e.g., amarker allele that positively correlates with tolerance) can be selectedfor, while plants that lack the locus, or that have a locus thatnegatively correlates with tolerance, can be selected against. Thus, inone method, subsequent to identification of a marker locus, the methodsinclude selecting (e.g., isolating) the first soybean plant orgermplasm, or selecting a progeny of the first plant or germplasm. Insome embodiments, the resulting selected first soybean plant orgermplasm can be crossed with a second soybean plant or germplasm (e.g.,an elite or exotic soybean, depending on characteristics that aredesired in the progeny).

Similarly, in other embodiments, if an allele is correlated withtolerance or improved tolerance to Fusarium solani infection, the methodcan include introgressing the allele into a second soybean plant orgermplasm to produce an introgressed soybean plant or germplasm. In someembodiments, the second soybean plant or germplasm will typicallydisplay reduced tolerance to Fusarium solani infection as compared tothe first soybean plant or germplasm, while the introgressed soybeanplant or germplasm will display an increased tolerance to Fusariumsolani infection as compared to the second plant or germplasm. Anintrogressed soybean plant or germplasm produced by these methods arealso a feature of the invention.

In other aspects, various mapping populations are used to determine thelinked markers of the invention. In one embodiment, the mappingpopulation used is the population derived from the cross P9362/93B41. Inother embodiments, other populations can be used, for example,93B72/93B68, 94B53/93B72 or 94M80/9492. In other aspects, varioussoftware can be used in determining linked marker loci. For example,TASSEL, GeneFlow and MapManager-QTX all find use with the invention. Insome embodiments, such as when software is used in the linkage analysis,the detected allele information (i.e., the data) is electronicallytransmitted or electronically stored, for example, in a computerreadable medium.

In addition to introgressing selected marker alleles into desiredgenetic backgrounds, transgenic approaches can also be used to produceFusarium solani tolerant soybean plants or germplasm. For example, insome aspects, the invention provides methods of producing a soybeanplant having tolerance or improved tolerance to Fusarium solaniinfection, the methods comprising introducing an exogenous nucleic acidinto a target soybean plant or progeny thereof, wherein the exogenousnucleic acid is derived from a nucleotide sequence that is linked to atleast one favorable allele of one or more marker locus that isassociated with tolerance or improved tolerance to Fusarium solaniinfection. In some embodiments, the marker locus can be selected from:SATT300, SATT591, SATT155, SATT266, SATT282, SATT412, SATT506, SATT355,SATT452, S60602-TB, SATT142, SATT181, SATT448, S60375-TB, SATT513,SATT549, SATT660, SATT339 and SATT255, as well as any other marker thatis closely linked (e.g., demonstrating not more than 10% recombinationfrequency) to these QTL markers; and furthermore, any marker locus thatis located within the chromosomal QTL intervals including:

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N).

In some embodiments, preferred QTL markers used in these transgenicplant methods are selected from SATT591, SATT155, SATT266, SATT412,SATT506, SATT355, SATT452, SATT549, SATT660, SATT339 and SATT255.

In some embodiments, a plurality of maker loci can be used to constructthe transgenic plant. Which QTL markers are used in combination is notparticularly limited. The QTL markers used in combinations can be any ofthe makers listed in FIG. 1, any other marker that is linked to themarkers in FIG. 1 (e.g., the linked markers as determined from FIGS. 4and 5, or determined from the SOYBASE resource), or any markers selectedfrom the QTL intervals described herein.

In some embodiments, the tolerance or improved tolerance is a non-racespecific tolerance or a non-race specific improved tolerance. In someaspects, the Fusarium solani is Fusarium solani f. sp. glycines.

Any of a variety of methods can be used to provide the exogenous nucleicacid to the soybean plant. In one method, the nucleotide sequence isisolated by positional cloning, and is identified by linkage to thefavorable allele. The precise composition of the exogenous nucleic acidcan vary; in one embodiment, the exogenous nucleic acid corresponds toan open reading frame (ORF) that encodes a polypeptide that, whenexpressed in a soybean plant, results in the soybean plant havingtolerance or improved tolerance to Fusarium solani infection. Theexogenous nucleic acid optionally comprises an expression vector toprovide for expression of the exogenous nucleic acid in the plant.

In other aspects, various mapping populations are used to determine thelinked markers that find use in constructing the transgenic plant. Inone embodiment, the mapping population used is the population derivedfrom the cross P9362/93B41. In other embodiments, other populations canbe used. In other aspects, various software and software parameters areused in determining linked marker loci used to construct the transgenicplant. For example, TASSEL, GeneFlow and MapManager-QTX all find usewith the invention.

Systems for identifying a soybean plant predicted to have tolerance orimproved tolerance to Fusarium solani infection are also a feature ofthe invention. Typically, the system can include a set of marker primersand/or probes configured to detect at least one favorable allele of oneor more marker locus associated with tolerance or improved tolerance toFusarium solani infection, wherein the marker locus or loci are selectedfrom: SATT300, SATT591, SATT155, SATT266, SATT282, SATT412, SATT506,SATT355, SATT452, S60602-TB, SATT142, SATT181, SATT448, S60375-TB,SATT513, SATT549, SATT660, SATT339 and SATT255, as well as any othermarker that is closely linked (e.g., demonstrating not more than 10%recombination frequency) to these QTL markers; and furthermore, anymarker locus that is located within the chromosomal QTL intervalsincluding:

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N).        In some embodiments, preferred QTL markers used in these        transgenic plant methods are selected from SATT591, SATT155,        SATT266, SATT412, SATT506, SATT355, SATT452, SATT549, SATT660,        SATT339 and SATT255.

Where a system that performs marker detection or correlation is desired,the system can also include a detector that is configured to detect oneor more signal outputs from the set of marker probes or primers, oramplicon thereof, thereby identifying the presence or absence of theallele; and/or system instructions that correlate the presence orabsence of the favorable allele with the predicted tolerance. Theprecise configuration of the detector will depend on the type of labelused to detect the marker allele. Typical embodiments include lightdetectors, radioactivity detectors, and the like. Detection of the lightemission or other probe label is indicative of the presence or absenceof a marker allele. Similarly, the precise form of the instructions canvary depending on the components of the system, e.g., they can bepresent as system software in one or more integrated unit of the system,or can be present in one or more computers or computer readable mediaoperably coupled to the detector. In one typical embodiment, the systeminstructions include at least one look-up table that includes acorrelation between the presence or absence of the favorable allele andpredicted tolerance, improved tolerance or susceptibility.

In some embodiments, the system can be comprised of separate elements orcan be integrated into a single unit for convenient detection of markersalleles and for performing marker-tolerance trait correlations. In someembodiments, the system can also include a sample, for example, genomicDNA, amplified genomic DNA, cDNA, amplified cDNA, RNA, or amplified RNAfrom soybean or from a selected soybean plant tissue.

Kits are also a feature of the invention. For example, a kit can includeappropriate primers or probes for detecting tolerance associated markerloci and instructions in using the primers or probes for detecting themarker loci and correlating the loci with predicted Fusarium solanitolerance. The kits can further include packaging materials forpackaging the probes, primers or instructions, controls such as controlamplification reactions that include probes, primers or template nucleicacids for amplifications, molecular size markers, or the like.

In other aspects, the invention provides nucleic acid compositions thatare the novel EST-derived SSR QTL markers of the invention. For example,the invention provides compositions comprising an amplification primerpair capable of initiating DNA polymerization by a DNA polymerase on asoybean nucleic acid template to generate a soybean marker amplicon,where the marker amplicon corresponds to a soybean marker selected fromS60602-TB and S60375-TB, and further where the composition comprises aprimer pair that is specific for the marker.

DEFINITIONS

Before describing the present invention in detail, it is to beunderstood that this invention is not limited to particular embodiments,which can, of course, vary. It is also to be understood that theterminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting. As used in thisspecification and the appended claims, terms in the singular and thesingular forms “a,” “an” and “the,” for example, include pluralreferents unless the content clearly dictates otherwise. Thus, forexample, reference to “plant,” “the plant” or “a plant” also includes aplurality of plants; also, depending on the context, use of the term“plant” can also include genetically similar or identical progeny ofthat plant; use of the term “a nucleic acid” optionally includes, as apractical matter, many copies of that nucleic acid molecule; similarly,the term “probe” optionally (and typically) encompasses many similar oridentical probe molecules.

Unless otherwise indicated, nucleic acids are written left to right in5′ to 3′ orientation. Numeric ranges recited within the specificationare inclusive of the numbers defining the range and include each integeror any non-integer fraction within the defined range. Unless definedotherwise, all technical and scientific terms used herein have the samemeaning as commonly understood by one of ordinary skill in the art towhich the invention pertains. Although any methods and materials similaror equivalent to those described herein can be used in the practice fortesting of the present invention, the preferred materials and methodsare described herein. In describing and claiming the present invention,the following terminology will be used in accordance with thedefinitions set out below.

A “plant” can be a whole plant, any part thereof, or a cell or tissueculture derived from a plant. Thus, the term “plant” can refer to anyof: whole plants, plant components or organs (e.g., leaves, stems,roots, etc.), plant tissues, seeds, plant cells, and/or progeny of thesame. A plant cell is a cell of a plant, taken from a plant, or derivedthrough culture from a cell taken from a plant. Thus, the term “soybeanplant” includes whole soybean plants, soybean plant cells, soybean plantprotoplast, soybean plant cell or soybean tissue culture from whichsoybean plants can be regenerated, soybean plant calli, soybean plantclumps and soybean plant cells that are intact in soybean plants orparts of soybean plants, such as soybean seeds, soybean pods, soybeanflowers, soybean cotyledons, soybean leaves, soybean stems, soybeanbuds, soybean roots, soybean root tips and the like.

“Germplasm” refers to genetic material of or from an individual (e.g., aplant), a group of individuals (e.g., a plant line, variety or family),or a clone derived from a line, variety, species, or culture. Thegermplasm can be part of an organism or cell, or can be separate fromthe organism or cell. In general, germplasm provides genetic materialwith a specific molecular makeup that provides a physical foundation forsome or all of the hereditary qualities of an organism or cell culture.As used herein, germplasm includes cells, seed or tissues from which newplants may be grown, or plant parts, such as leafs, stems, pollen, orcells, that can be cultured into a whole plant.

The term “allele” refers to one of two or more different nucleotidesequences that occur at a specific locus. For example, a first allelecan occur on one chromosome, while a second allele occurs on a secondhomologous chromosome, e.g., as occurs for different chromosomes of aheterozygous individual, or between different homozygous or heterozygousindividuals in a population. A “favorable allele” is the allele at aparticular locus that confers, or contributes to, an agronomicallydesirable phenotype, e.g., tolerance to Fusarium solani infection, oralternatively, is an allele that allows the identification ofsusceptible plants that can be removed from a breeding program orplanting. A favorable allele of a marker is a marker allele thatsegregates with the favorable phenotype, or alternatively, segregateswith susceptible plant phenotype, therefore providing the benefit ofidentifying disease-prone plants. A favorable allelic form of achromosome segment is a chromosome segment that includes a nucleotidesequence that contributes to superior agronomic performance at one ormore genetic loci physically located on the chromosome segment. “Allelefrequency” refers to the frequency (proportion or percentage) at whichan allele is present at a locus within an individual, within a line, orwithin a population of lines. For example, for an allele “A,” diploidindividuals of genotype “AA,” “Aa,” or “aa” have allele frequencies of1.0, 0.5, or 0.0, respectively. One can estimate the allele frequencywithin a line by averaging the allele frequencies of a sample ofindividuals from that line. Similarly, one can calculate the allelefrequency within a population of lines by averaging the allelefrequencies of lines that make up the population. For a population witha finite number of individuals or lines, an allele frequency can beexpressed as a count of individuals or lines (or any other specifiedgrouping) containing the allele.

An allele “positively” correlates with a trait when it is linked to itand when presence of the allele is an indictor that the desired trait ortrait form will occur in a plant comprising the allele. An allelenegatively correlates with a trait when it is linked to it and whenpresence of the allele is an indicator that a desired trait or traitform will not occur in a plant comprising the allele.

An individual is “homozygous” if the individual has only one type ofallele at a given locus (e.g., a diploid individual has a copy of thesame allele at a locus for each of two homologous chromosomes). Anindividual is “heterozygous” if more than one allele type is present ata given locus (e.g., a diploid individual with one copy each of twodifferent alleles). The term “homogeneity” indicates that members of agroup have the same genotype at one or more specific loci. In contrast,the term “heterogeneity” is used to indicate that individuals within thegroup differ in genotype at one or more specific loci.

A “locus” is a chromosomal region where a polymorphic nucleic acid,trait determinant, gene or marker is located. Thus, for example, a “genelocus” is a specific chromosome location in the genome of a specieswhere a specific gene can be found.

The term “quantitative trait locus” or “QTL” refers to a polymorphicgenetic locus with at least two alleles that differentially affect theexpression of a phenotypic trait in at least one genetic background,e.g., in at least one breeding population or progeny.

The terms “marker,” “molecular marker,” “marker nucleic acid,” and“marker locus” refer to a nucleotide sequence or encoded product thereof(e.g., a protein) used as a point of reference when identifying a linkedlocus. A marker can be derived from genomic nucleotide sequence or fromexpressed nucleotide sequences (e.g., from a spliced RNA, a cDNA, etc.),or from an encoded polypeptide. The term also refers to nucleic acidsequences complementary to or flanking the marker sequences, such asnucleic acids used as probes or primer pairs capable of amplifying themarker sequence. A “marker probe” is a nucleic acid sequence or moleculethat can be used to identify the presence of a marker locus, e.g., anucleic acid probe that is complementary to a marker locus sequence.Alternatively, in some aspects, a marker probe refers to a probe of anytype that is able to distinguish (i.e., genotype) the particular allelethat is present at a marker locus. Nucleic acids are “complementary”when they specifically hybridize in solution, e.g., according toWatson-Crick base pairing rules. A “marker locus” is a locus that can beused to track the presence of a second linked locus, e.g., a linkedlocus that encodes or contributes to expression of a phenotypic trait.For example, a marker locus can be used to monitor segregation ofalleles at a locus, such as a QTL, that are genetically or physicallylinked to the marker locus. Thus, a “marker allele,” alternatively an“allele of a marker locus” is one of a plurality of polymorphicnucleotide sequences found at a marker locus in a population that ispolymorphic for the marker locus. In some aspects, the present inventionprovides marker loci correlating with tolerance to Fusarium solaniinfection in soybean. Each of the identified markers is expected to bein close physical and genetic proximity (resulting in physical and/orgenetic linkage) to a genetic element, e.g., a QTL, that contributes totolerance.

“Genetic markers” are nucleic acids that are polymorphic in a populationand where the alleles of which can be detected and distinguished by oneor more analytic methods, e.g., RFLP, AFLP, isozyme, SNP, SSR, and thelike. The terms “genetic marker” and “molecular marker” refer to agenetic locus (a “marker locus”) that can be used as a point ofreference when identifying a genetically linked locus such as a QTL.Such a marker is also referred to as a QTL marker. The term also refersto nucleic acid sequences complementary to the genomic sequences, suchas nucleic acids used as probes.

Markers corresponding to genetic polymorphisms between members of apopulation can be detected by methods well-established in the art. Theseinclude, e.g., PCR-based sequence specific amplification methods,detection of restriction fragment length polymorphisms (RFLP), detectionof isozyme markers, detection of polynucleotide polymorphisms by allelespecific hybridization (ASH), detection of amplified variable sequencesof the plant genome, detection of self-sustained sequence replication,detection of simple sequence repeats (SSRs), detection of singlenucleotide polymorphisms (SNPs), or detection of amplified fragmentlength polymorphisms (AFLPs). Well established methods are also know forthe detection of expressed sequence tags (ESTs) and SSR markers derivedfrom EST sequences and randomly amplified polymorphic DNA (RAPD).

A “genetic map” is a description of genetic linkage relationships amongloci on one or more chromosomes (or linkage groups) within a givenspecies, generally depicted in a diagrammatic or tabular form. “Geneticmapping” is the process of defining the linkage relationships of locithrough the use of genetic markers, populations segregating for themarkers, and standard genetic principles of recombination frequency. A“genetic map location” is a location on a genetic map relative tosurrounding genetic markers on the same linkage group where a specifiedmarker can be found within a given species. In contrast, a physical mapof the genome refers to absolute distances (for example, measured inbase pairs or isolated and overlapping contiguous genetic fragments,e.g., contigs). A physical map of the genome does not take into accountthe genetic behavior (e.g., recombination frequencies) between differentpoints on the physical map.

A “genetic recombination frequency” is the frequency of a crossing overevent (recombination) between two genetic loci. Recombination frequencycan be observed by following the segregation of markers and/or traitsfollowing meiosis. A genetic recombination frequency can be expressed incentimorgans (cM), where one cM is the distance between two geneticmarkers that show a 1% recombination frequency (i.e., a crossing-overevent occurs between those two markers once in every 100 celldivisions).

As used herein, the term “linkage” is used to describe the degree withwhich one marker locus is “associated with” another marker locus or someother locus (for example, a tolerance locus).

As used herein, linkage equilibrium describes a situation where twomarkers independently segregate, i.e., sort among progeny randomly.Markers that show linkage equilibrium are considered unlinked (whetheror not they lie on the same chromosome).

As used herein, linkage disequilibrium describes a situation where twomarkers segregate in a non-random manner, i.e., have a recombinationfrequency of less than 50% (and by definition, are separated by lessthan 50 cM on the same linkage group). Markers that show linkagedisequilibrium are considered linked. Linkage occurs when the markerlocus and a linked locus are found together in progeny plants morefrequently than not together in the progeny plants. As used herein,linkage can be between two markers, or alternatively between a markerand a phenotype. A marker locus can be associated with (linked to) atrait, e.g., a marker locus can be associated with tolerance or improvedtolerance to a plant pathogen when the marker locus is in linkagedisequilibrium with the tolerance trait. The degree of linkage of amolecular marker to a phenotypic trait (e.g., a QTL) is measured, e.g.,as a statistical probability of co-segregation of that molecular markerwith the phenotype.

As used herein, the linkage relationship between a molecular marker anda phenotype is given as a “probability” or “adjusted probability.” Theprobability value is the statistical likelihood that the particularcombination of a phenotype and the presence or absence of a particularmarker allele is random. Thus, the lower the probability score, thegreater the likelihood that a phenotype and a particular marker willco-segregate. In some aspects, the probability score is considered“significant” or “nonsignificant.” In some embodiments, a probabilityscore of 0.05 (p=0.05, or a 5% probability) of random assortment isconsidered a significant indication of co-segregation. However, thepresent invention is not limited to this particular standard, and anacceptable probability can be any probability of less than 50% (p=0.5).For example, a significant probability can be less than 0.25, less than0.20, less than 0.15, or less than 0.1.

The term “linkage disequilibrium” refers to a non-random segregation ofgenetic loci or traits (or both). In either case, linkage disequilibriumimplies that the relevant loci are within sufficient physical proximityalong a length of a chromosome so that they segregate together withgreater than random (i.e., non-random) frequency (in the case ofco-segregating traits, the loci that underlie the traits are insufficient proximity to each other). Linked loci co-segregate more than50% of the time, e.g., from about 51% to about 100% of the time. Theterm “physically linked” is sometimes used to indicate that two loci,e.g., two marker loci, are physically present on the same chromosome.

Advantageously, the two linked loci are located in close proximity suchthat recombination between homologous chromosome pairs does not occurbetween the two loci during meiosis with high frequency, e.g., such thatlinked loci co-segregate at least about 90% of the time, e.g., 91%, 92%,93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.75%, or more of the time.

The phrase “closely linked,” in the present application, means thatrecombination between two linked loci occurs with a frequency of equalto or less than about 10% (i.e., are separated on a genetic map by notmore than 10 cM). Put another way, the closely linked loci co-segregateat least 90% of the time. Marker loci are especially useful in thepresent invention when they demonstrate a significant probability ofco-segregation (linkage) with a desired trait (e.g., pathogenictolerance). For example, in some aspects, these markers can be termedlinked QTL markers. In other aspects, especially useful molecularmarkers are those markers that are linked or closely linked to QTLmarkers.

In some aspects, linkage can be expressed as any desired limit or range.For example, in some embodiments, two linked loci are two loci that areseparated by less than 50 cM map units. In other embodiments, linkedloci are two loci that are separated by less than 40 cM. In otherembodiments, two linked loci are two loci that are separated by lessthan 30 cM. In other embodiments, two linked loci are two loci that areseparated by less than 25 cM. In other embodiments, two linked loci aretwo loci that are separated by less than 20 cM. In other embodiments,two linked loci are two loci that are separated by less than 15 cM. Insome aspects, it is advantageous to define a bracketed range of linkage,for example, between 10 and 20 cM, or between 10 and 30 cM, or between10 and 40 cM.

The more closely a marker is linked to a second locus, the better anindicator for the second locus that marker becomes. Thus, in oneembodiment, closely linked loci such as a marker locus and a secondlocus (e.g., a QTL marker) display an inter-locus recombinationfrequency of 10% or less, preferably about 9% or less, still morepreferably about 8% or less, yet more preferably about 7% or less, stillmore preferably about 6% or less, yet more preferably about 5% or less,still more preferably about 4% or less, yet more preferably about 3% orless, and still more preferably about 2% or less. In highly preferredembodiments, the relevant loci (e.g., a marker locus and a QTL marker)display a recombination a frequency of about 1% or less, e.g., about0.75% or less, more preferably about 0.5% or less, or yet morepreferably about 0.25% or less. Two loci that are localized to the samechromosome, and at such a distance that recombination between the twoloci occurs at a frequency of less than 10% (e.g., about 9%, 8%, 7%, 6%,5%, 4%, 3%, 2%, 1%, 0.75%, 0.5%, 0.25%, or less) are also said to be“proximal to” each other. In some cases, two different markers can havethe same genetic map coordinates. In that case, the two markers are insuch close proximity to each other that recombination occurs betweenthem with such low frequency that it is undetectable.

When referring to the relationship between two genetic elements, such asa genetic element contributing to tolerance and a proximal marker,“coupling” phase linkage indicates the state where the “favorable”allele at the tolerance locus is physically associated on the samechromosome strand as the “favorable” allele of the respective linkedmarker locus. In coupling phase, both favorable alleles are inheritedtogether by progeny that inherit that chromosome strand. In “repulsion”phase linkage, the “favorable” allele at the locus of interest (e.g., aQTL for tolerance) is physically linked with an “unfavorable” allele atthe proximal marker locus, and the two “favorable” alleles are notinherited together (i.e., the two loci are “out of phase” with eachother).

As used herein, the terms “chromosome interval” or “chromosome segment”designate a contiguous linear span of genomic DNA that resides in plantaon a single chromosome. The genetic elements or genes located on asingle chromosome interval are physically linked. The size of achromosome interval is not particularly limited.

In some aspects, for example in the context of the present invention,generally the genetic elements located within a single chromosomeinterval are also genetically linked, typically within a geneticrecombination distance of, for example, less than or equal to 20centimorgan (cM), or alternatively, less than or equal to 10 cM. Thatis, two genetic elements within a single chromosome interval undergorecombination at a frequency of less than or equal to 20% or 10%

In one aspect, any marker of the invention is linked (genetically andphysically) to any other marker that is at or less than 50 cM distant.In another aspect, any marker of the invention is closely linked(genetically and physically) to any other marker that is in closeproximity, e.g., at or less than 10 cM distant. Two closely linkedmarkers on the same chromosome can be positioned 9, 8, 7, 6, 5, 4, 3, 2,1, 0.75, 0.5 or 0.25 cM or less from each other.

“Tolerance” or “improved tolerance” in a soybean plant to Fusariumsolani infection is an indication that the soybean plant is lessaffected with respect to yield and/or survivability or other relevantagronomic measures, upon infection by Fusarium solani, than a lesstolerant or more “susceptible” plant. Tolerance is a relative term,indicating that the infected plant produces better yield of soybean thananother similarly infected more susceptible plant. That is, theinfection causes a reduced decrease in soybean survival and/or yield ina tolerant soybean plant, as compared to a susceptible soybean plant.One of skill will appreciate that soybean plant tolerance to Fusariumsolani infection varies widely, and that tolerance also will varydepending on the severity of the infection.

However, by simple observation, one of skill can determine the relativetolerance or susceptibility of different plants, plant lines or plantfamilies to Fusarium solani infection of a given severity, and use thatinformation to compare the relative tolerances of soybean lines acrossmultiple locations and growth seasons. For example, an infectionseverity system can be established based on foliar scorch, suddenwilting and death of the plant during the growing season. See also,Gibson (1994) “Soybean varietal response to sudden death syndrome,” pp20-40 in D. Wilkinson (ed.) Proc. Twenty-Fourth Soybean Seed Res. Conf.Chicago Ill. for Am Seed Trade Assoc., Washington D.C.; and Rupe et al.(1991) Plant Dis. 75:47-50). In one typical example, plants are assignedtolerance rating of between 9 (highly tolerant, yield and survivabilitynot significantly affected by infection) to 1 (plants are totallynecrotic). In one such example scale, 9=No disease; 8=very slightsymptoms including virus like crinkling and small chlorotic spots;7=larger chlorotic spots on less than 20% of the leaves; 6=browning andcoalescing of spots; 5=extensive browning and curling of top leaves;4=leaves dropping, lower leaves browning and curling; 3=top stem dying,lower leaves dropping; 2=middle stem dying; 1=plants are totallynecrotic (dried up plant skeletons). This scale is optionally reversedat the discretion of the practitioner, i.e., with 1=to no disease and9=to totally necrotic plants; see also, Njiti et al. (2003) “RoundupReady Soybean: Glyphosate Effects on Fusarium solani Root Colonizationand Sudden Death Syndrome” Agron. J. 95(5):1140-1145. One of skill willappreciate that other scales for symptoms can also be used if desired.

Fusarium solani “tolerance” differs from Fusarium solani “resistance” inthat tolerance is a measure of a soybean plant's ability to survive andyield soybean despite the presence of Fusarium solani infection, asopposed to a measure of the soybean plant's ability to resist infection.As used in the art, “tolerance” is sometimes referred to as “generalresistance,” “rate-reducing resistance” or “partial resistance.”

Resistance to Fusarium solani is often “race-specific.” That is, overtime, a population (e.g., a race) of Fusarium solani evolves to overcomea resistance trait in a given line of soybean. Once this occurs, theresistance trait is “race specific” in that the resistance trait is nolonger effective at resisting infection by the evolved Fusarium solanipopulation (that is, the evolved Fusarium solani population is a “race”that is not blocked from achieving a productive infection by theresistance trait). Tolerance, on the other hand, can sometimes be“non-race specific” in that populations of Fusarium solani are notnecessarily selected to overcome tolerance, because a tolerant soybeanplant permits the Fusarium solani pathogen to achieve a productiveinfection.

The term “crossed” or “cross” in the context of this invention means thefusion of gametes via pollination to produce progeny (e.g., cells, seedsor plants). The term encompasses both sexual crosses (the pollination ofone plant by another) and selfing (self-pollination, e.g., when thepollen and ovule are from the same plant).

The term “introgression” refers to the transmission of a desired alleleof a genetic locus from one genetic background to another. For example,introgression of a desired allele at a specified locus can betransmitted to at least one progeny via a sexual cross between twoparents of the same species, where at least one of the parents has thedesired allele in its genome. Alternatively, for example, transmissionof an allele can occur by recombination between two donor genomes, e.g.,in a fused protoplast, where at least one of the donor protoplasts hasthe desired allele in its genome. The desired allele can be, e.g., aselected allele of a marker, a QTL, a transgene, or the like. In anycase, offspring comprising the desired allele can be repeatedlybackcrossed to a line having a desired genetic background and selectedfor the desired allele, to result in the allele becoming fixed in aselected genetic background.

A “line” or “strain” is a group of individuals of identical parentagethat are generally inbred to some degree and that are generallyhomozygous and homogeneous at most loci (isogenic or near isogenic). A“subline” refers to an inbred subset of descendents that are geneticallydistinct from other similarly inbred subsets descended from the sameprogenitor. Traditionally, a “subline” has been derived by inbreedingthe seed from an individual soybean plant selected at the F3 to F5generation until the residual segregating loci are “fixed” or homozygousacross most or all loci. Commercial soybean varieties (or lines) aretypically produced by aggregating (“bulking”) the self-pollinatedprogeny of a single F3 to F5 plant from a controlled cross between 2genetically different parents. While the variety typically appearsuniform, the self-pollinating variety derived from the selected planteventually (e.g., F8) becomes a mixture of homozygous plants that canvary in genotype at any locus that was heterozygous in the originallyselected F3 to F5 plant. In the context of the invention, marker-basedsublines, that differ from each other based on qualitative polymorphismat the DNA level at one or more specific marker loci, are derived bygenotyping a sample of seed derived from individual self-pollinatedprogeny derived from a selected F3-F5 plant. The seed sample can begenotyped directly as seed, or as plant tissue grown from such a seedsample. Optionally, seed sharing a common genotype at the specifiedlocus (or loci) are bulked providing a subline that is geneticallyhomogenous at identified loci important for a trait of interest (yield,tolerance, etc.).

An “ancestral line” is a parent line used as a source of genes e.g., forthe development of elite lines. An “ancestral population” is a group ofancestors that have contributed the bulk of the genetic variation thatwas used to develop elite lines. “Descendants” are the progeny ofancestors, and may be separated from their ancestors by many generationsof breeding. For example, elite lines are the descendants of theirancestors. A “pedigree structure” defines the relationship between adescendant and each ancestor that gave rise to that descendant. Apedigree structure can span one or more generations, describingrelationships between the descendant and it's parents, grand parents,great-grand parents, etc.

An “elite line” or “elite strain” is an agronomically superior line thathas resulted from many cycles of breeding and selection for superioragronomic performance. Numerous elite lines are available and known tothose of skill in the art of soybean breeding. An “elite population” isan assortment of elite individuals or lines that can be used torepresent the state of the art in terms of agronomically superiorgenotypes of a given crop species, such as soybean. Similarly, an “elitegermplasm” or elite strain of germplasm is an agronomically superiorgermplasm, typically derived from and/or capable of giving rise to aplant with superior agronomic performance, such as an existing or newlydeveloped elite line of soybean.

In contrast, an “exotic soybean strain” or an “exotic soybean germplasm”is a strain or germplasm derived from a soybean not belonging to anavailable elite soybean line or strain of germplasm. In the context of across between two soybean plants or strains of germplasm, an exoticgermplasm is not closely related by descent to the elite germplasm withwhich it is crossed. Most commonly, the exotic germplasm is not derivedfrom any known elite line of soybean, but rather is selected tointroduce novel genetic elements (typically novel alleles) into abreeding program.

The term “amplifying” in the context of nucleic acid amplification isany process whereby additional copies of a selected nucleic acid (or atranscribed form thereof) are produced. Typical amplification methodsinclude various polymerase based replication methods, including thepolymerase chain reaction (PCR), ligase mediated methods such as theligase chain reaction (LCR) and RNA polymerase based amplification(e.g., by transcription) methods. An “amplicon” is an amplified nucleicacid, e.g., a nucleic acid that is produced by amplifying a templatenucleic acid by any available amplification method (e.g., PCR, LCR,transcription, or the like).

A “genomic nucleic acid” is a nucleic acid that corresponds in sequenceto a heritable nucleic acid in a cell. Common examples include nucleargenomic DNA and amplicons thereof. A genomic nucleic acid is, in somecases, different from a spliced RNA, or a corresponding cDNA, in thatthe spliced RNA or cDNA is processed, e.g., by the splicing machinery,to remove introns. Genomic nucleic acids optionally comprisenon-transcribed (e.g., chromosome structural sequences, promoterregions, enhancer regions, etc.) and/or non-translated sequences (e.g.,introns), whereas spliced RNA/cDNA typically do not have non-transcribedsequences or introns. A “template nucleic acid” is a nucleic acid thatserves as a template in an amplification reaction (e.g., a polymerasebased amplification reaction such as PCR, a ligase mediatedamplification reaction such as LCR, a transcription reaction, or thelike). A template nucleic acid can be genomic in origin, oralternatively, can be derived from expressed sequences, e.g., a cDNA oran EST.

An “exogenous nucleic acid” is a nucleic acid that is not native to aspecified system (e.g., a germplasm, plant, variety, etc.), with respectto sequence, genomic position, or both. As used herein, the terms“exogenous” or “heterologous” as applied to polynucleotides orpolypeptides typically refers to molecules that have been artificiallysupplied to a biological system (e.g., a plant cell, a plant gene, aparticular plant species or variety or a plant chromosome under study)and are not native to that particular biological system. The terms canindicate that the relevant material originated from a source other thana naturally occurring source, or can refer to molecules having anon-natural configuration, genetic location or arrangement of parts.

In contrast, for example, a “native” or “endogenous” gene is a gene thatdoes not contain nucleic acid elements encoded by sources other than thechromosome or other genetic element on which it is normally found innature. An endogenous gene, transcript or polypeptide is encoded by itsnatural chromosomal locus, and not artificially supplied to the cell.

The term “recombinant” in reference to a nucleic acid or polypeptideindicates that the material (e.g., a recombinant nucleic acid, gene,polynucleotide, polypeptide, etc.) has been altered by humanintervention. Generally, the arrangement of parts of a recombinantmolecule is not a native configuration, or the primary sequence of therecombinant polynucleotide or polypeptide has in some way beenmanipulated. The alteration to yield the recombinant material can beperformed on the material within or removed from its natural environmentor state. For example, a naturally occurring nucleic acid becomes arecombinant nucleic acid if it is altered, or if it is transcribed fromDNA which has been altered, by means of human intervention performedwithin the cell from which it originates. A gene sequence open readingframe is recombinant if that nucleotide sequence has been removed fromit natural context and cloned into any type of artificial nucleic acidvector. Protocols and reagents to produce recombinant molecules,especially recombinant nucleic acids, are common and routine in the art.The term recombinant can also refer to an organism that harborsrecombinant material, e.g., a plant that comprises a recombinant nucleicacid is considered a recombinant plant. In some embodiments, arecombinant organism is a transgenic organism.

The term “introduced” when referring to translocating a heterologous orexogenous nucleic acid into a cell refers to the incorporation of thenucleic acid into the cell using any methodology. The term encompassessuch nucleic acid introduction methods as “transfection,”“transformation” and “transduction.”

As used herein, the term “vector” is used in reference to polynucleotideor other molecules that transfer nucleic acid segment(s) into a cell.The term “vehicle” is sometimes used interchangeably with “vector.” Avector optionally comprises parts which mediate vector maintenance andenable its intended use (e.g., sequences necessary for replication,genes imparting drug or antibiotic resistance, a multiple cloning site,operably linked promoter/enhancer elements which enable the expressionof a cloned gene, etc.). Vectors are often derived from plasmids,bacteriophages, or plant or animal viruses. A “cloning vector” or“shuttle vector” or “subcloning vector” contains operably linked partsthat facilitate subcloning steps (e.g., a multiple cloning sitecontaining multiple restriction endonuclease sites).

The term “expression vector” as used herein refers to a vectorcomprising operably linked polynucleotide sequences that facilitateexpression of a coding sequence in a particular host organism (e.g., abacterial expression vector or a plant expression vector).Polynucleotide sequences that facilitate expression in prokaryotestypically include, e.g., a promoter, an operator (optional), and aribosome binding site, often along with other sequences. Eukaryoticcells can use promoters, enhancers, termination and polyadenylationsignals and other sequences that are generally different from those usedby prokaryotes.

The term “transgenic plant” refers to a plant that comprises within itscells a heterologous polynucleotide. Generally, the heterologouspolynucleotide is stably integrated within the genome such that thepolynucleotide is passed on to successive generations. The heterologouspolynucleotide may be integrated into the genome alone or as part of arecombinant expression cassette. “Transgenic” is used herein to refer toany cell, cell line, callus, tissue, plant part or plant, the genotypeof which has been altered by the presence of heterologous nucleic acidincluding those transgenic organisms or cells initially so altered, aswell as those created by crosses or asexual propagation from the initialtransgenic organism or cell. The term “transgenic” as used herein doesnot encompass the alteration of the genome (chromosomal orextra-chromosomal) by conventional plant breeding methods (e.g.,crosses) or by naturally occurring events such as randomcross-fertilization, non-recombinant viral infection, non-recombinantbacterial transformation, non-recombinant transposition, or spontaneousmutation.

“Positional cloning” is a cloning procedure in which a target nucleicacid is identified and isolated by its genomic proximity to markernucleic acid. For example, a genomic nucleic acid clone can include partor all of two more chromosomal regions that are proximal to one another.If a marker can be used to identify the genomic nucleic acid clone froma genomic library, standard methods such as sub-cloning or sequencingcan be used to identify and or isolate subsequences of the clone thatare located near the marker.

A specified nucleic acid is “derived from” a given nucleic acid when itis constructed using the given nucleic acid's sequence, or when thespecified nucleic acid is constructed using the given nucleic acid. Forexample, a cDNA or EST is derived from an expressed mRNA.

The term “genetic element” or “gene” refers to a heritable sequence ofDNA, i.e., a genomic sequence, with functional significance. The term“gene” can also be used to refer to, e.g., a cDNA and/or a mRNA encodedby a genomic sequence, as well as to that genomic sequence.

The term “genotype” is the genetic constitution of an individual (orgroup of individuals) at one or more genetic loci, as contrasted withthe observable trait (the phenotype). Genotype is defined by theallele(s) of one or more known loci that the individual has inheritedfrom its parents. The term genotype can be used to refer to anindividual's genetic constitution at a single locus, at multiple loci,or, more generally, the term genotype can be used to refer to anindividual's genetic make-up for all the genes in its genome. A“haplotype” is the genotype of an individual at a plurality of geneticloci. Typically, the genetic loci described by a haplotype arephysically and genetically linked, i.e., on the same chromosome segment.

The terms “phenotype,” or “phenotypic trait” or “trait” refers to one ormore trait of an organism. The phenotype can be observable to the nakedeye, or by any other means of evaluation known in the art, e.g.,microscopy, biochemical analysis, genomic analysis, an assay for aparticular disease resistance, etc. In some cases, a phenotype isdirectly controlled by a single gene or genetic locus, i.e., a “singlegene trait.” In other cases, a phenotype is the result of several genes.A “quantitative trait loci” (QTL) is a genetic domain that ispolymorphic and effects a phenotype that can be described inquantitative terms, e.g., height, weight, oil content, days togermination, disease resistance, etc, and, therefore, can be assigned a“phenotypic value” which corresponds to a quantitative value for thephenotypic trait. A QTL can act through a single gene mechanism or by apolygenic mechanism.

A “molecular phenotype” is a phenotype detectable at the level of apopulation of (one or more) molecules. Such molecules can be nucleicacids such as genomic DNA or RNA, proteins, or metabolites. For example,a molecular phenotype can be an expression profile for one or more geneproducts, e.g., at a specific stage of plant development, in response toan environmental condition or stress, etc. Expression profiles aretypically evaluated at the level of RNA or protein, e.g., on a nucleicacid array or “chip” or using antibodies or other binding proteins.

The term “yield” refers to the productivity per unit area of aparticular plant product of commercial value. For example, yield ofsoybean is commonly measured in bushels of seed per acre or metric tonsof seed per hectare per season. Yield is affected by both genetic andenvironmental factors. “Agronomics,” “agronomic traits,” and “agronomicperformance” refer to the traits (and underlying genetic elements) of agiven plant variety that contribute to yield over the course of growingseason. Individual agronomic traits include emergence vigor, vegetativevigor, stress tolerance, disease resistance or tolerance, herbicideresistance, branching, flowering, seed set, seed size, seed density,standability, threshability and the like. Yield is, therefore, the finalculmination of all agronomic traits.

A “set” of markers or probes refers to a collection or group of markersor probes, or the data derived therefrom, used for a common purpose,e.g., identifying soybean plants with a desired trait (e.g., toleranceto Fusarium solani infection). Frequently, data corresponding to themarkers or probes, or data derived from their use, is stored in anelectronic medium. While each of the members of a set possess utilitywith respect to the specified purpose, individual markers selected fromthe set as well as subsets including some, but not all of the markers,are also effective in achieving the specified purpose.

A “look up table” is a table that correlates one form of data toanother, or one or more forms of data with a predicted outcome that thedata is relevant to. For example, a look up table can include acorrelation between allele data and a predicted trait that a plantcomprising a given allele is likely to display. These tables can be, andtypically are, multidimensional, e.g., taking multiple alleles intoaccount simultaneously, and, optionally, taking other factors intoaccount as well, such as genetic background, e.g., in making a traitprediction.

A “computer readable medium” is an information storage media that can beaccessed by a computer using an available or custom interface. Examplesinclude memory (e.g., ROM or RAM, flash memory, etc.), optical storagemedia (e.g., CD-ROM), magnetic storage media (computer hard drives,floppy disks, etc.), punch cards, and many others that are commerciallyavailable. Information can be transmitted between a system of interestand the computer, or to or from the computer to or from the computerreadable medium for storage or access of stored information. Thistransmission can be an electrical transmission, or can be made by otheravailable methods, such as an IR link, a wireless connection, or thelike.

“System instructions” are instruction sets that can be partially orfully executed by the system. Typically, the instruction sets arepresent as system software.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 provides a table listing soybean markers demonstrating linkagedisequilibrium with Fusarium solani infection tolerance phenotype asdetermined by intergroup allele frequency distribution analysis,association mapping analysis and QTL interval mapping (including singlemarker regression analysis) methods. The table indicates the genomic-SSRor EST-SSR marker type (all simple sequence repeats), the chromosome onwhich the marker is located and its approximate genetic map positionrelative to other known markers, given in cM, with position zero beingthe first (most distal) marker on the chromosome, as provided in theintegrated genetic map in FIG. 5. Also shown are the soybean populationsused in the analysis and the statistical probability of randomsegregation of the marker and the tolerance phenotype given as anadjusted probability taking into account the variability and falsepositives of multiple tests. Results from QTL interval mapping areprovided, with the significance values given as a likelihood ratiostatistic (LRS).

FIG. 2 provides a table listing the genomic and EST SSR markers thatdemonstrated linkage disequilibrium with the Fusarium solani infectiontolerance phenotype and the sequences of the left and right PCR primersused in the SSR marker locus genotyping analysis. Also shown is thepigtail sequence used on the 5′ end of the right primer, and the numberof nucleotides in the tandem repeating element in the SSR.

FIG. 3 provides an allele dictionary of the characterized alleles of theSSR markers that demonstrated linkage disequilibrium with the Fusariumsolani infection tolerance phenotype. Each allele is defined by the sizeof a PCR amplicon generated from soybean genomic DNA or mRNA using theprimers listed in FIG. 2. Sizes of the PCR amplicons are indicated inbase pairs (bp).

FIG. 4 provides a table listing genetic markers that are closely linkedto the Fusarium solani tolerance markers identified by the presentinvention.

FIG. 5 provides an integrated genetic map for approximately 750 soybeanmarkers, including both SSR-type and SNP-type markers. These markers aredistributed over each soybean chromosome. The chromosome number, as wellas the equivalent historical chromosome name are indicated. The geneticmap positions of the markers are indicated in centiMorgans (cM),typically with position zero being the first (most distal) marker on thechromosome.

DETAILED DESCRIPTION

Sudden Death Syndrome (SDS), caused by, e.g., Fusarium solani (e.g.,Fusarium solani f.sp glycines and/or Fusarium solani f.sp phaseoli), isa major disease of soybean, causing severe losses in soybean viabilityand overall yield. Fusarium solani tolerant soybean cultivars have beenproduced in an attempt to reduce these losses, e.g., the cultivarsForrest, Pyramid and Essex. However, the strong selective pressures thatresistant soybean impose on Fusarium solani cause relatively rapid lossof resistance against races of Fusarium solani that evolve to combatresistance traits in the resistant soybean. Accordingly, tolerance toFusarium solani infection, in which the plant survives, thrives andproduces high yields, despite a productive Fusarium solani infection, isan alternate strategy to combat losses due to Fusarium solani infection.An advantage to tolerance, as compared simply to resistance, is that itis less likely to result in races of Fusarium solani that combat thetolerance traits, as the tolerant plants simply support a productiveinfection while maintaining high yield, regardless of the race ofFusarium solani at issue (tolerance can, therefore, be “non-racespecific”). Thus, while it is possible that races of Fusarium solani mayevolve to take advantage of the tolerance traits in Fusarium solanitolerant soybean in some manner, it is clear that the evolutionarypressures on both Fusarium solani and soybean are quite different thanwith a resistance phenotype. That is, there is not a strong negativeselection against Fusarium solani imposed by tolerance, because tolerantsoybean plants support a productive Fusarium solani infection.

The identification and selection of soybean plants that show toleranceto Fusarium solani infection using MAS can provide an effective andenvironmentally friendly approach to overcoming losses caused by thisdisease. The present invention provides soybean marker loci thatdemonstrate statistically significant co-segregation with Fusariumsolani tolerance. Detection of these loci or additional linked loci canbe used in marker assisted soybean breeding programs to produce tolerantplants, or plants with improved tolerance. The linked SSR markersidentified herein are provided in FIG. 1. These markers include SATT300,SATT591, SATT155, SATT266, SATT282, SATT412, SATT506, SATT355, SATT452,S60602-TB, SATT142, SATT181, SATT448, S60375-TB, SATT513, SATT549,SATT660, SATT339 and SATT255.

Each of the SSR-type markers display a plurality of alleles that can bevisualized as different sized PCR amplicons, as summarized in the SSRallele dictionary in FIG. 3. The PCR primers that are used to generatethe SSR-marker amplicons are provided in FIG. 2. The alleles of SNP-typemarkers are determined using an allele-specific hybridization protocol,as known in the art.

As recognized in the art, any other marker that is linked to a QTLmarker (e.g., a disease tolerance marker) also finds use for that samepurpose. Examples of additional markers that are linked to the diseasetolerance markers recited herein are provided. For example, a linkedmarker can be determined from the soybean consensus genetic map providedin FIG. 5. Additional closely linked markers are further provided inFIG. 4. It is not intended, however, that linked markers finding usewith the invention be limited to those recited in FIG. 4 or 5.

The invention also provides chromosomal QTL intervals that correlatewith Fusarium solani infection tolerance. These intervals are located onlinkage groups B1, G, K and M. Any marker located within these intervalsfinds use as a marker for Fusarium solani infection tolerance. Theseintervals include:

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N).

Methods for identifying soybean plants or germplasm that carry preferredalleles of tolerance marker loci are a feature of the invention. Inthese methods, any of a variety of marker detection protocols are usedto identify marker loci, depending on the type of marker loci. Typicalmethods for marker detection include amplification and detection of theresulting amplified markers, e.g., by PCR, LCR, transcription basedamplification methods, or the like. These include ASH, SSR detection,RFLP analysis and many others.

Although particular marker alleles can show co-segregation with adisease tolerance or susceptibility phenotype, it is important to notethat the marker locus is not necessarily part of the QTL locusresponsible for the tolerance or susceptibility. For example, it is nota requirement that the marker polynucleotide sequence be part of a genethat imparts disease resistance (for example, be part of the gene openreading frame). The association between a specific marker allele withthe tolerance or susceptibility phenotype is due to the original“coupling” linkage phase between the marker allele and the QTL toleranceor susceptibility allele in the ancestral soybean line from which thetolerance or susceptibility allele originated. Eventually, with repeatedrecombination, crossing over events between the marker and QTL locus canchange this orientation. For this reason, the favorable marker allelemay change depending on the linkage phase that exists within thetolerant parent used to create segregating populations. This does notchange the fact the genetic marker can be used to monitor segregation ofthe phenotype. It only changes which marker allele is consideredfavorable in a given segregating population.

Identification of soybean plants or germplasm that include a markerlocus or marker loci linked to a tolerance trait or traits provides abasis for performing marker assisted selection of soybean. Soybeanplants that comprise favorable markers or favorable alleles are selectedfor, while soybean plants that comprise markers or alleles that arenegatively correlated with tolerance can be selected against. Desiredmarkers and/or alleles can be introgressed into soybean having a desired(e.g., elite or exotic) genetic background to produce an introgressedtolerant soybean plant or germplasm. In some aspects, it is contemplatedthat a plurality of tolerance markers are sequentially or simultaneousselected and/or introgressed. The combinations of tolerance markers thatare selected for in a single plant is not limited, and can include anycombination of markers recited in FIG. 1, any markers linked to themarkers recited in FIG. 1, or any markers located within the QTLintervals defined herein.

As an alternative to standard breeding methods of introducing traits ofinterest into soybean (e.g., introgression), transgenic approaches canalso be used. In these methods, exogenous nucleic acids that encodetraits linked to markers are introduced into target plants or germplasm.For example, a nucleic acid that codes for a tolerance trait is cloned,e.g., via positional cloning and introduced into a target plant orgermplasm.

Verification of tolerance can be performed by available toleranceprotocols, as discussed in more detail below. For example, suchprotocols can be found in Li et al. (1998) “Chlamydospore formation,production, and nuclear status in Fusarium solani f. sp. glycinessoybean sudden death syndrome-causing isolates.” Mycologia 90:414-421,and Njiti et al. (2003) “Roundup Ready Soybean: Glyphosate Effects onFusarium solani Root Colonization and Sudden Death Syndrome.” Agron. J.95(5): 1140-1145. Tolerance assays are useful to verify that thetolerance trait still segregates with the marker in any particular plantor population, and, of course, to measure the degree of toleranceimprovement achieved by introgressing or recombinantly introducing thetrait into a desired background.

Systems, including automated systems for selecting plants that comprisea marker of interest and/or for correlating presence of the marker withtolerance are also a feature of the invention. These systems can includeprobes relevant to marker locus detection, detectors for detectinglabels on the probes, appropriate fluid handling elements andtemperature controllers that mix probes and templates and/or amplifytemplates, and systems instructions that correlate label detection tothe presence of a particular marker locus or allele.

Kits are also a feature of the invention. For example, a kit can includeappropriate primers or probes for detecting tolerance associated markerloci and instructions in using the primers or probes for detecting themarker loci and correlating the loci with predicted Fusarium solanitolerance. The kits can further include packaging materials forpackaging the probes, primers or instructions, controls such as controlamplification reactions that include probes, primers or template nucleicacids for amplifications, molecular size markers, or the like.

Tolerance Markers and Favorable Alleles

In traditional linkage analysis, no direct knowledge of the physicalrelationship of genes on a chromosome is required. Mendel's first law isthat factors of pairs of characters are segregated, meaning that allelesof a diploid trait separate into two gametes and then into differentoffspring. Classical linkage analysis can be thought of as a statisticaldescription of the relative frequencies of cosegregation of differenttraits. Linkage analysis is the well characterized descriptive frameworkof how traits are grouped together based upon the frequency with whichthey segregate together. That is, if two non-allelic traits areinherited together with a greater than random frequency, they are saidto be “linked.” The frequency with which the traits are inheritedtogether is the primary measure of how tightly the traits are linked,i.e., traits which are inherited together with a higher frequency aremore closely linked than traits which are inherited together with lower(but still above random) frequency. Traits are linked because the geneswhich underlie the traits reside on the same chromosome. The furtherapart on a chromosome the genes reside, the less likely they are tosegregate together, because homologous chromosomes recombine duringmeiosis. Thus, the further apart on a chromosome the genes reside, themore likely it is that there will be a crossing over event duringmeiosis that will result in two genes segregating separately intoprogeny.

A common measure of linkage is the frequency with which traitscosegregate. This can be expressed as a percentage of cosegregation(recombination frequency) or, also commonly, in centiMorgans (cM). ThecM is named after the pioneering geneticist Thomas Hunt Morgan and is aunit of measure of genetic recombination frequency. One cM is equal to a1% chance that a trait at one genetic locus will be separated from atrait at another locus due to crossing over in a single generation(meaning the traits segregate together 99% of the time). Becausechromosomal distance is approximately proportional to the frequency ofcrossing over events between traits, there is an approximate physicaldistance that correlates with recombination frequency. For example, insoybean, 1 cM correlates, on average, to about 400,000 base pairs (400Kb).

Marker loci are themselves traits and can be assessed according tostandard linkage analysis by tracking the marker loci duringsegregation. Thus, in the context of the present invention, one cM isequal to a 1% chance that a marker locus will be separated from anotherlocus (which can be any other trait, e.g., another marker locus, oranother trait locus that encodes a QTL), due to crossing over in asingle generation. The markers herein, as described in FIG. 1, e.g.,SATT300, SATT591, SATT155, SATT266, SATT282, SATT412, SATT506, SATT355,SATT452, S60602-TB, SATT142, SATT181, SATT448, S60375-TB, SATT513,SATT549, SATT660, SATT339 and SATT255, as well as any of the chromosomeintervals

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N),        have been found to correlate with tolerance, improved tolerance        or susceptibility to Fusarium solani infection in soybean. This        means that the markers are sufficiently proximal to a tolerance        trait that they can be used as a predictor for the tolerance        trait. This is extremely useful in the context of marker        assisted selection (MAS), discussed in more detail herein. In        brief, soybean plants or germplasm can be selected for markers        or marker alleles that positively correlate with tolerance,        without actually raising soybean and measuring for tolerance or        improved tolerance (or, contrawise, soybean plants can be        selected against if they possess markers that negatively        correlate with tolerance or improved tolerance). MAS is a        powerful shortcut to selecting for desired phenotypes and for        introgressing desired traits into cultivars of soybean (e.g.,        introgressing desired traits into elite lines). MAS is easily        adapted to high throughput molecular analysis methods that can        quickly screen large numbers of plant or germplasm genetic        material for the markers of interest and is much more cost        effective than raising and observing plants for visible traits.

In some embodiments, the most preferred QTL markers are a subset of themarkers provided in FIG. 1. For example, the most preferred markers canbe selected from SATT591, SATT155, SATT266, SATT412, SATT506, SATT355,SATT452, SATT549, SATT660, SATT339 and SATT255.

When referring to the relationship between two genetic elements, such asa genetic element contributing to tolerance and a proximal marker,“coupling” phase linkage indicates the state where the “favorable”allele at the tolerance locus is physically associated on the samechromosome strand as the “favorable” allele of the respective linkedmarker locus. In coupling phase, both favorable alleles are inheritedtogether by progeny that inherit that chromosome strand. In “repulsion”phase linkage, the “favorable” allele at the locus of interest (e.g., aQTL for tolerance) is physically linked with an “unfavorable” allele atthe proximal marker locus, and the two “favorable” alleles are notinherited together (i.e., the two loci are “out of phase” with eachother).

A favorable allele of a marker is that allele of the marker thatco-segregates with a desired phenotype (e.g., disease tolerance). Asused herein, a QTL marker has a minimum of one favorable allele,although it is possible that the marker might have two or more favorablealleles found in the population. Any favorable allele of that marker canbe used advantageously for the identification and construction oftolerant soybean lines. Optionally, one, two, three or more favorableallele(s) of different markers are identified in, or introgressed into aplant, and can be selected for or against during MAS. Desirably, plantsor germplasm are identified that have at least one such favorable allelethat positively correlates with tolerance or improved tolerance.

Alternatively, a marker allele that co-segregates with diseasesusceptibility also finds use with the invention, since that allele canbe used to identify and counter select disease-susceptible plants. Suchan allele can be used for exclusionary purposes during breeding toidentify alleles that negatively correlate with tolerance, to eliminatesusceptible plants or germplasm from subsequent rounds of breeding.

In some embodiments of the invention, a plurality of marker alleles aresimultaneously selected for in a single plant or a population of plants.In these methods, plants are selected that contain favorable allelesfrom more than one tolerance marker, or alternatively, favorable allelesfrom more than one tolerance marker are introgressed into a desiredsoybean germplasm. One of skill in the art recognizes that thesimultaneous selection of favorable alleles from more than one diseasetolerance marker in the same plant is likely to result in an additive(or even synergistic) protective effect for the plant.

One of skill recognizes that the identification of favorable markeralleles is germplasm-specific. The determination of which marker allelescorrelate with tolerance (or susceptibility) is determined for theparticular germplasm under study. One of skill recognizes that methodsfor identifying the favorable alleles are routine and well known in theart, and furthermore, that the identification and use of such favorablealleles is well within the scope of the invention. Furthermore still,identification of favorable marker alleles in soybean populations otherthan the populations used or described herein is well within the scopeof the invention.

Amplification primers for amplifying SSR-type marker loci are a featureof the invention. FIG. 2 provides specific primers for marker locusamplification. However, one of skill will immediately recognize thatother sequences to either side of the given primers can be used in placeof the given primers, so long as the primers can amplify a region thatincludes the allele to be detected. Further, it will be appreciated thatthe precise probe to be used for detection can vary, e.g., any probethat can identify the region of a marker amplicon to be detected can besubstituted for those examples provided herein. Further, theconfiguration of the amplification primers and detection probes can, ofcourse, vary. Thus, the invention is not limited to the primers andprobes specifically recited herein.

In some aspects, methods of the invention utilize an amplification stepto detect/genotype a marker locus. However, it will be appreciated thatamplification is not a requirement for marker detection—for example, onecan directly detect unamplified genomic DNA simply by performing aSouthern blot on a sample of genomic DNA. Procedures for performingSouthern blotting, amplification (PCR, LCR, or the like) and many othernucleic acid detection methods are well established and are taught,e.g., in Sambrook et al., Molecular Cloning—A Laboratory Manual (3rdEd.), Vol. 1-3, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.,2000 (“Sambrook”); Current Protocols in Molecular Biology, F. M. Ausubelet al., eds., Current Protocols, a joint venture between GreenePublishing Associates, Inc. and John Wiley & Sons, Inc., (supplementedthrough 2002) (“Ausubel”)) and PCR Protocols A Guide to Methods andApplications (Innis et al. eds) Academic Press Inc. San Diego, Calif.(1990) (Innis). Additional details regarding detection of nucleic acidsin plants can also be found, e.g., in Plant Molecular Biology (1993)Croy (ed.) BIOS Scientific Publishers, Inc.

Separate detection probes can also be omitted in amplification/detectionmethods, e.g., by performing a real time amplification reaction thatdetects product formation by modification of the relevant amplificationprimer upon incorporation into a product, incorporation of labelednucleotides into an amplicon, or by monitoring changes in molecularrotation properties of amplicons as compared to unamplified precursors(e.g., by fluorescence polarization).

Typically, molecular markers are detected by any established methodavailable in the art, including, without limitation, allele specifichybridization (ASH) or other methods for detecting single nucleotidepolymorphisms (SNP), amplified fragment length polymorphism (AFLP)detection, amplified variable sequence detection, randomly amplifiedpolymorphic DNA (RAPD) detection, restriction fragment lengthpolymorphism (RFLP) detection, self-sustained sequence replicationdetection, simple sequence repeat (SSR) detection, single-strandconformation polymorphisms (SSCP) detection, isozyme markers detection,or the like. While the exemplary markers provided in the figures andtables herein are either SSR or SNP (ASH) markers, any of theaforementioned marker types can be employed in the context of theinvention to identify chromosome segments encompassing genetic elementthat contribute to superior agronomic performance (e.g., tolerance orimproved tolerance).

QTL Chromosome Intervals

In some aspects, the invention provides QTL chromosome intervals, wherea QTL (or multiple QTLs) that segregate with Fusarium solani diseasetolerance are contained in those intervals. A variety of methods wellknown in the art are available for identifying chromosome intervals(also as described in detail in EXAMPLE 3). The boundaries of suchchromosome intervals are drawn to encompass markers that will be linkedto one or more QTL. In other words, the chromosome interval is drawnsuch that any marker that lies within that interval (including theterminal markers that define the boundaries of the interval) can be usedas markers for disease tolerance. Each interval comprises at least oneQTL, and furthermore, may indeed comprise more than one QTL. Closeproximity of multiple QTL in the same interval may obfuscate thecorrelation of a particular marker with a particular QTL, as one markermay demonstrate linkage to more than one QTL. Conversely, e.g., if twomarkers in close proximity show co-segregation with the desiredphenotypic trait, it is sometimes unclear if each of those markersidentifying the same QTL or two different QTL. Regardless, knowledge ofhow many QTL are in a particular interval is not necessary to make orpractice the invention.

The present invention provides soybean chromosome intervals, where themarkers within that interval demonstrate co-segregation with toleranceto Fusarium solani infection. Thus, each of these intervals comprises atleast one Fusarium solani tolerance QTL. These intervals are:

Linkage Method(s) of Group Flanking Markers Identification A1 SATT300 toSATT155 Marker Clustering D1b SATT282 to SATT506 Marker Clustering NSATT549 to SATT255 QTL Interval Mapping and Marker Clustering

Each of the intervals described above shows a clustering of markers thatco-segregate with Fusarium solani disease tolerance. This clustering ofmarkers occurs in relatively small domains on the linkage groups,indicating the presence of one or more QTL in those chromosome regions.QTL intervals were drawn to encompass the markers that co-segregate withpathogen tolerance. The intervals are defined by the markers on theirtermini, where the interval encompasses all the markers that map withinthe interval as well as the markers that define the termini.

In one case, one of the intervals that was drawn on LG-N by a markerclustering effect (observed in single marker regression analysis) wasfurther independently confirmed by a QTL mapping analysis, as describedin detail in EXAMPLE 3. In those experiments, markers within that domainof LG-N show a significant likelihood ratio statistic (LRS) for thepresence of one or more QTL responsible for the Fusarium solanitolerance trait on that region of the chromosome.

Genetic Maps

As one of skill in the art will recognize, recombination frequencies(and as a result, genetic map positions) in any particular populationare not static. The genetic distances separating two markers (or amarker and a QTL) can vary depending on how the map positions aredetermined. For example, variables such as the parental mappingpopulations used, the software used in the marker mapping or QTLmapping, and the parameters input by the user of the mapping softwarecan contribute to the QTL/marker genetic map relationships. However, itis not intended that the invention be limited to any particular mappingpopulations, use of any particular software, or any particular set ofsoftware parameters to determine linkage of a particular marker orchromosome interval with the Fusarium solani tolerance phenotype. It iswell within the ability of one of ordinary skill in the art toextrapolate the novel features described herein to any soybean gene poolor population of interest, and using any particular software andsoftware parameters. Indeed, observations regarding tolerance markersand chromosome intervals in populations in additions to those describedherein are readily made using the teaching of the present disclosure.

Mapping Populations

Any suitable soybean strains can be used to generate mapping data or formarker association studies. A large number of commonly used soybeanlines (e.g., commercial varieties) and mapping populations are known inthe art. Additional strains finding use with the invention are alsodescribed in the present disclosure. Useful soybean mapping populationsand lines include but are not limited to:

Mapping Population Description/Reference UP1C6-43 × 90B73 UP1C6-43 is apublic line from the University of Nebraska.. 90B73 is described inPlant Variety Protection Act, Certificate No. 200000152 for Soybean‘90B73’ issued May 8, 2001; see also, U.S. Pat. No. 6,316,700, issuedNov. 13, 2001, to Hedges. P1082 × 90B73 P1082 is described in PlantVariety Protection Act, Certificate No. 8200115, issued May 26, 1982.90B73 is described in Plant Variety Protection Act, Certificate No.200000152 for Soybean ‘90B73’ issued May 8, 2001; see also, U.S. Pat.No. 6,316,700, issued Nov. 13, 2001, to Hedges. Minsoy × Noir 1Recombinant Inbred Line (RIL) population derived by single seed descent,consisting of 240 F7-derived RILs. Described in Lark et al., (1993) “Agenetic map of soybean (Glycine max L.) and using an intraspecific crossof two cultivars: Minosy and Noir 1,” Theor. Appl. Genet., 86: 901-906;Mansur and Orf (1995) “Evaluation of soybean recombinant inbreds foragronomic performance in northern USA and Chile,” Crop Sci., 35:422-425; Mansur et al., (1996) “Genetic mapping of agronomic traitsusing recombinant inbred lines of soybean,” Crop Sci., 36: 1327-1336.Developed at the University of Utah. See also Intl. Patent Appl. No. WO98/49887, filed May 1, 1998. Minsoy × Archer RIL population derived bysingle seed descent, consisting of 233 F7- derived RILs. Described inMansur and Orf (1995) “Evaluation of soybean recombinant inbreds foragronomic performance in northern USA and Chile,” Crop Sci., 35:422-425; Mansur et al., (1996) “Genetic mapping of agronomic traitsusing recombinant inbred lines of soybean,” Crop Sci., 36: 1327-1336.Developed at the University of Utah. See also Intl. Patent Appl. No. WO98/49887, filed May 1, 1998. Noir 1 × Archer RIL Population derived bysingle seed descent, consisting of 240 F7- derived RILs. Described inMansur and Orf (1995) “Evaluation of soybean recombinant inbreds foragronomic performance in northern USA and Chile,” Crop Sci., 35:422-425; Mansur et al., (1996) “Genetic mapping of agronomic traitsusing recombinant inbred lines of soybean,” Crop Sci., 36: 1327-1336.Developed at the University of Utah. See also Intl. Patent Appl. No. WO98/49887, filed May 1, 1998. Clark × Harosoy Population derived from thecross of near isogenic lines (NILs) of the cultivars Clark and Harosoy.The population consists of derivatives of 57 F2 plants (see, Shoemakerand Specht (1995) “Integration of the soybean molecular and classicalgenetic linkage groups,” Crop Sci., 35: 436-446). Developed at theUniversity of Nebraska. A81-356022 × PI468916 This is an F2-derivedmapping population from the interspecific cross of the A81-356022(Glycine max) and PI468.916 (G. soja). The population consists of 59 F2plant derivatives and has been described in detail (Keim et al., (1990)“RFLP mapping in soybean: association between marker loci and variationin quantitative traits,” Genetics 126: 735-742; Shoemaker and Specht(1995) “Integration of the soybean molecular and classical geneticlinkage groups,” Crop Sci., 35: 436-446; Shoemaker and Olson (1993)Molecular linkage map of soybean (Glycine max L. Merr.). p.6.131-6.138,in Genetic maps: Locus maps of complex genomes [O'Brien (ed.)] ColdSpring Harbor Laboratory Press, New York). Commonly referred to as theUSDA/Iowa State University Population (MS). OX715 × P9242 OX715 is apublic variety. P9242 is described in Plant Variety Protection Act,Certificate No. 9300238 for Soybean ‘9242’ issued May 30, 1997. Sloan,Williams, Harosoy and See, Burnham et al., Crop Sci., “QuantitativeTrait Loci for Partial Conrad Resistance to Phytophthora sojae inSoybean,” 43: 1610-1617 (various RILs derived from (2003); Weiss andStevenson, Agron. J., 47: 541-543 (1955); crosses of the abovecultivars) Bernard and Lindahl, Crop Sci., 43: 101-105 (1972); Bahrenfusand Fehr, Crop Sci., 20: 673 (1980); Fehr et al., Crop Sci., 29: 830(1989). Bert, Marcus, Corsoy, A92- See, Glover and Scott, “Heritabilityand Phenotypic Variation of 627030, Simpson, OT92-1, Tolerance toPhytophthora Root Rot of Soybean,” Crop Sci., Hendricks, Freeborn,Surge, 38: 1495-1500 (1998); and additional references made therein.Kenwood 94 (various RILs derived from crosses of the above cultivars)Essex × Forrest See, Yuan et al., “Quantitative trait loci in twosoybean recombinant Flyer × Hartwig inbred line populations segregatingfor yield and disease resistance,” Crop Sci., 42: 271-277 (2002).Williams × PI399073 US Patent Appl. No. 2004/0034890, published Feb. 19,2004; US S 19-90 × PI399073 Patent Appl. No. 2004/0261144, publishedDec. 23, 2004. 9163 × 92B05 P9163 is a commercially available Pioneervariety described in Plant Variety Protection Act, Certificate No.9600053. 92B05 is a commercially available Pioneer variety described inPlant Variety Protection Act, Certificate No. 9900092 for Soybean‘92B05’ issued Sep. 21, 2000; see also, U.S. Pat. No. 5,942,668, issuedAug. 24, 1999 to Grace et al. 9362 × 93B41 P9362 is a commerciallyavailable Pioneer variety described in Plant Variety Protection Act,Certificate No. 9400098. 93B41 is a commercially available Pioneervariety described in Plant Variety Protection Act, Certificate No.9800068; see also, U.S. Pat. No. 5,750,853, issued May 12, 1998 toFuller et al. 93B35 Described in Plant Variety Protection Act,Certificate No. 200000035, issued Apr. 24, 2001. See also, U.S. Pat. No.6,153,818, issued Nov. 28, 2000. 93B53 Described in Plant VarietyProtection Act, Certificate No. 9900101, issued Oct. 27, 2000. See also,U.S. Pat. No. 6,075,182, issued Jun. 13, 2000. 93M11 Described in PlantVariety Protection Act, Certificate No. 200400080, issued Aug. 16, 2004.See also, U.S. Pat. No. 6,855,875, issued Feb. 15, 2005. 93B68 Describedin Plant Variety Protection Act, Certificate No. 200200084, issued Jun.10, 2002. See also, US Patent Appl. Ser. No. 10/271,115. 93B72 Describedin Plant Variety Protection Act, Certificate No. 200100071, issued May8, 2001. See also, U.S. Pat. No. 6,566,589, issued May 20, 2003. 94B53Described in Plant Variety Protection Act, Certificate No. 200000031,issued May 8, 2001. See also, U.S. Pat. No. 6,235,976, issued May 22,2001. 94M80 Described in pending Plant Variety Protection Act,Certificate No. 200500084, filed Jan. 18, 2005. See also, pending USPatent Appl. Ser. No. 10/768,275, filed Jan. 30, 2005. 9492 Described inPlant Variety Protection Act, Certificate No. 9800077, issued Sep.12,2001. See also, U.S. Pat. No. 5,792,907, issued Aug. 11, 1998.

Mapping Software

A variety of commercial software is available for genetic mapping andmarker association studies (e.g., QTL mapping). This software includesbut is not limited to:

Software Description/References JoinMap ® VanOoijen, and Voorrips (2001)“JoinMap 3.0 software for the calculation of genetic linkage maps,”Plant Research International, Wageningen, the Netherlands; and, Stam“Construction of integrated genetic linkage maps by means of a newcomputer package: JoinMap,” The Plant Journal 3(5): 739-744 (1993)MapQTL ® J. W. vanOoijen, “Software for the mapping of quantitativetrait loci in experimental populations,” Kyazma B. V., Wageningen,Netherlands MapManager QT Manly and Olson, “Overview of QTL mappingsoftware and introduction to Map Manager QT,” Mamm. Genome 10: 327-334(1999) MapManager QTX Manly, Cudmore and Meer, “MapManager QTX,cross-platform software for genetic mapping,” Mamm. Genome 12: 930-932(2001) GeneFlow ® and GENEFLOW, Inc. (Alexandria, VA) QTLocate ™ TASSEL(Trait Analysis by aSSociation, Evolution, and Linkage) by EdwardBuckler, and information about the program can be found on the BucklerLab web page at the Institute for Genomic Diversity at CornellUniversity.

Unified Genetic Maps

“Unified,” “consensus” or “integrated” genetic maps have been createdthat incorporate mapping data from two or more sources, includingsources that used different mapping populations and different modes ofstatistical analysis. The merging of genetic map information increasesthe marker density on the map, as well as improving map resolution.These improved maps can be advantageously used in marker assistedselection, map-based cloning, provide an improved framework forpositioning newly identified molecular markers and aid in theidentification of QTL chromosome intervals and clusters ofadvantageously-linked markers.

In some aspects, a consensus map is derived by simply overlaying one mapon top of another. In other aspects, various algorithms, e.g., JoinMap®analysis, allows the combination of genetic mapping data from multiplesources, and reconciles discrepancies between mapping data from theoriginal sources. See, Van Ooijen, and Voorrips (2001) “JoinMap 3.0software for the calculation of genetic linkage maps,” Plant ResearchInternational, Wageningen, the Netherlands; and, Stam (1993)“Construction of integrated genetic linkage maps by means of a newcomputer package: JoinMap,” The Plant Journal 3(5):739-744.

FIG. 5 provides a composite genetic map that incorporates mappinginformation from various sources. This map was derived using theUSDA/Iowa State University mapping population data (as described inCregan et al., “An Integrated Genetic Linkage Map of the Soybean Genome”Crop Science 39:1464-1490 [1999]; and see references therein) as aframework. Additional markers, as they became known, have beencontinuously added to that map, including public SSR markers,EST-derived markers, and SNP markers. This map contains approximately750 soybean markers that are distributed over each of the soybeanchromosomes. The markers that are on this map are known in the art(i.e., have been previously described; see, e.g., the SOYBASE on-lineresource for extensive listings of these markers and descriptions of theindividual markers) or are described herein.

Additional integrated maps are known in the art. See, e.g., Cregan etal., “An Integrated Genetic Linkage Map of the Soybean Genome” CropScience 39:1464-1490 (1999); and also International Application No.PCT/US2004/024919 by Sebastian, filed Jul. 27, 2004, entitled “SoybeanPlants Having Superior Agronomic Performance and Methods for theirProduction”).

Song et al. provides another integrated soybean genetic map thatincorporates mapping information from five different mapping populations(Song et al., “A New Integrated Genetic Linkage Map of the Soybean,”Theor. Appl. Genet., 109:122-128 [2004]). This integrated map containsapproximately 1,800 soybean markers, including SSR and SNP-type markers,as well as EST markers, RPLP markers, AFLP, RAPD, isozyme and classicalmarkers (e.g., seed coat color). The markers that are on this map areknown in the art and have been previously characterized. Thisinformation is also available at the website for the Soybean Genomicsand Improvement Laboratory (SGIL) at the USDA Beltsville AgriculturalResearch Center (BARC). See, specifically, the description of projectsin the Cregan Laboratory on that website.

The soybean integrated linkage map provided in Song et al. (2004) isbased on the principle described by Stam (1993) “Construction ofintegrated genetic linkage maps by means of a new computer package:JoinMap,” The Plant Journal 3(5):739-744; and Van Ooijen and Voorrips(2001) “JoinMap 3.0 software for the calculation of genetic linkagemaps,” Plant Research International, Wageningen, the Netherlands.Mapping information from five soybean populations was used in the mapintegration, and also used to place recently identified SSR markers ontothe soybean genome. These mapping populations were Minsoy×Noir 1 (MN),Minsoy×Archer (MA), Noir 1×Archer (NA), Clark×Harosoy (CH) andA81-356022×PI468916 (MS). The JoinMap® analysis resulted in a map with20 linkage groups containing a total of 1849 markers, including 1015SSRs, 709 RFLPs, 73 RAPDs, 24 classical traits, six AFLPs, ten isozymesand 12 others. Among the mapped SSR markers were 417 previouslyuncharacterized SSRs.

Initially, LOD scores and pairwise recombination frequencies betweenmarkers were calculated. A LOD of 5.0 was used to create groups in theMS, MA, NA populations and LOD 4.0 in the MN and CH populations. The mapof each linkage group was then integrated. Recombination values wereconverted to genetic distances using the Kosambi mapping function.

Linked Markers

From the present disclosure and widely recognized in the art, it isclear that any genetic marker that has a significant probability ofco-segregation with a phenotypic trait of interest (e.g., in the presentcase, a pathogen tolerance or improved tolerance trait) can be used as amarker for that trait. As list of useful QTL markers provided by thepresent invention is provided in FIG. 1.

In addition to the QTL markers noted in FIG. 1, additional markerslinked to (showing linkage disequilibrium with) the QTL markers can alsobe used to predict the tolerance or improved tolerance trait in asoybean plant. In other words, any other marker showing less than 50%recombination frequency (separated by a genetic distance less than 50cM) with a QTL marker of the invention (e.g., the markers provided inFIG. 1) is also a feature of the invention. Any marker that is linked toa QTL marker can also be used advantageously in marker-assistedselection for the particular trait.

Genetic markers that are linked to QTL markers (e.g., QTL markersprovided in FIG. 1) are particularly useful when they are sufficientlyproximal (e.g., closely linked) to a given QTL marker so that thegenetic marker and the QTL marker display a low recombination frequency.In the present invention, such closely linked markers are a feature ofthe invention. As defined herein, closely linked markers display arecombination frequency of about 10% or less (the given marker is within10 cM of the QTL). Put another way, these closely linked locico-segregate at least 90% of the time. Indeed, the closer a marker is toa QTL marker, the more effective and advantageous that marker becomes asan indicator for the desired trait.

Thus, in other embodiments, closely linked loci such as a QTL markerlocus and a second locus display an inter-locus cross-over frequency ofabout 10% or less, preferably about 9% or less, still more preferablyabout 8% or less, yet more preferably about 7% or less, still morepreferably about 6% or less, yet more preferably about 5% or less, stillmore preferably about 4% or less, yet more preferably about 3% or less,and still more preferably about 2% or less. In highly preferredembodiments, the relevant loci (e.g., a marker locus and a target locussuch as a QTL) display a recombination a frequency of about 1% or less,e.g., about 0.75% or less, more preferably about 0.5% or less, or yetmore preferably about 0.25% or less. Thus, the loci are about 10 cM, 9cM, 8 cM, 7 cM, 6 cM, 5 cM, 4 cM, 3 cM, 2 cM, 1 cM, 0.75 cM, 0.5 cM or0.25 cM or less apart. Put another way, two loci that are localized tothe same chromosome, and at such a distance that recombination betweenthe two loci occurs at a frequency of less than 10% (e.g., about 9%, 8%,7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.75%, 0.5%, 0.25%, or less) are said to be“proximal to” each other.

In some aspects, linked markers (including closely linked markers) ofthe invention are determined by review of a genetic map, for example,the integrated genetic map shown in FIG. 5. For example, it is shownherein that the linkage group D1b marker SATT506 correlates with atleast one Fusarium solani tolerance QTL. Markers that are linked toSATT506 can be determined from the map provided in FIG. 5. For example,markers on linkage group A1 that are closely linked to SATT506 include:

Map Linkage Position Marker Group (cM) SATT282 D1b 64.3 SATT290 D1b 64.3SATT428 D1b 64.3 SATT579 D1b 64.3 SATT005 D1b 65.1 SATT412 D1b 65.1SATT537 D1b 65.1 SATT600 D1b 65.1 SATT141 D1b 65.9 SATT189 D1b 65.9SATT506 D1b 65.9 SATT604 D1b 65.9 P10637A-1 D1b 66.0 SATT350 D1b 66.2SAT_135 D1b 67.0 SATT041 D1b 72.0

Similarly, linked markers (including closely linked markers) of theinvention can be determined by review of any suitable soybean geneticmap. For example, the integrated genetic map described in Song et al.(2004) also provides a means to identify linked (including closelylinked) markers. See, Song et al., “A New Integrated Genetic Linkage Mapof the Soybean,” Theor. Appl. Genet., 109:122-128 [2004]; see also thewebsite for the Soybean Genomics and Improvement Laboratory (SGIL) atthe USDA Beltsville Agricultural Research Center (BARC), and seespecifically the description of projects in the Cregan Laboratory onthat website. That genetic map incorporates a variety of genetic markersthat are known in the art or alternatively are described in thatreference. Detailed descriptions of numerous markers, including many ofthose described in Song et al. (2004) can be found at the SOYBASEwebsite resource.

For example, according to the Song et al. (2004) integrated genetic map,markers on linkage group A1 that are closely linked to SATT506 include:

Sat_(—)423, A747_(—)1, Sat_(—)135, Satt412, Satt141, Satt290, Satt611,Satt604, K011_(—)4, Satt506, Satt005, Satt600, L050_(—)3, Satt537,Satt579, Satt282, Sat_(—)089, Satt189, Satt350, Sat428, Mng137_(—)1,Bng047_(—)1, Sat_(—)169, Satt644 and Satt041.

It is not intended that the determination of linked or closely linkedmarkers be limited to the use of any particular soybean genetic map.Indeed, a large number of soybean genetic maps is available and are wellknown to one of skill in the art. Another map that finds use with theinvention in this respect is the integrated soybean genetic maps foundon the SOYBASE website resource. Alternatively still, the determinationof linked and closely linked markers can be made by the generation of anexperimental dataset and linkage analysis.

It is not intended that the identification of markers that are linked(e.g., within about 50 cM or within about 10 cM) to the Fusarium solanitolerance QTL markers identified herein be limited to any particular mapor methodology. The integrated genetic map provided in FIG. 5 servesonly as example for identifying linked markers. Indeed, linked markersas defined herein can be determined from any genetic map known in theart (an experimental map or an integrated map), or alternatively, can bedetermined from any new mapping dataset.

It is noted that lists of linked and closely linked markers may varybetween maps and methodologies due to various factors. First, themarkers that are placed on any two maps may not be identical, andfurthermore, some maps may have a greater marker density than anothermap. Also, the mapping populations, methodologies and algorithms used toconstruct genetic maps can differ. One of skill in the art recognizesthat one genetic map is not necessarily more or less accurate thananother, and furthermore, recognizes that any soybean genetic map can beused to determine markers that are linked and closely linked to the QTLmarkers of the present invention.

Techniques for Marker Detection

The invention provides molecular markers that have a significantprobability of co-segregation with QTL that impart a Fusarium solanitolerance phenotype. These QTL markers find use in marker assistedselection for desired traits (tolerance or improved tolerance), and alsohave other uses. It is not intended that the invention be limited to anyparticular method for the detection of these markers.

Markers corresponding to genetic polymorphisms between members of apopulation can be detected by numerous methods well-established in theart (e.g., PCR-based sequence specific amplification, restrictionfragment length polymorphisms (RFLPs), isozyme markers, allele specifichybridization (ASH), amplified variable sequences of the plant genome,self-sustained sequence replication, simple sequence repeat (SSR),single nucleotide polymorphism (SNP), random amplified polymorphic DNA(“RAPD”) or amplified fragment length polymorphisms (AFLP). In oneadditional embodiment, the presence or absence of a molecular marker isdetermined simply through nucleotide sequencing of the polymorphicmarker region. This method is readily adapted to high throughputanalysis as are the other methods noted above, e.g., using availablehigh throughput sequencing methods such as sequencing by hybridization.

In general, the majority of genetic markers rely on one or more propertyof nucleic acids for their detection. For example, some techniques fordetecting genetic markers utilize hybridization of a probe nucleic acidto nucleic acids corresponding to the genetic marker (e.g., amplifiednucleic acids produced using genomic soybean DNA as a template).Hybridization formats, including but not limited to solution phase,solid phase, mixed phase, or in situ hybridization assays are useful forallele detection. An extensive guide to the hybridization of nucleicacids is found in Tijssen (1993) Laboratory Techniques in Biochemistryand Molecular Biology—Hybridization with Nucleic Acid Probes Elsevier,N.Y., as well as in Sambrook, Berger and Ausubel (herein).

For example, markers that comprise restriction fragment lengthpolymorphisms (RFLP) are detected, e.g., by hybridizing a probe which istypically a sub-fragment (or a synthetic oligonucleotide correspondingto a sub-fragment) of the nucleic acid to be detected to restrictiondigested genomic DNA. The restriction enzyme is selected to providerestriction fragments of at least two alternative (or polymorphic)lengths in different individuals or populations. Determining one or morerestriction enzyme that produces informative fragments for each cross isa simple procedure, well known in the art. After separation by length inan appropriate matrix (e.g., agarose or polyacrylamide) and transfer toa membrane (e.g., nitrocellulose, nylon, etc.), the labeled probe ishybridized under conditions which result in equilibrium binding of theprobe to the target followed by removal of excess probe by washing.

Nucleic acid probes to the marker loci can be cloned and/or synthesized.Any suitable label can be used with a probe of the invention. Detectablelabels suitable for use with nucleic acid probes include, for example,any composition detectable by spectroscopic, radioisotopic,photochemical, biochemical, immunochemical, electrical, optical orchemical means. Useful labels include biotin for staining with labeledstreptavidin conjugate, magnetic beads, fluorescent dyes, radiolabels,enzymes, and colorimetric labels. Other labels include ligands whichbind to antibodies labeled with fluorophores, chemiluminescent agents,and enzymes. A probe can also constitute radiolabelled PCR primers thatare used to generate a radiolabelled amplicon. Labeling strategies forlabeling nucleic acids and corresponding detection strategies can befound, e.g., in Haugland (1996) Handbook of Fluorescent Probes andResearch Chemicals Sixth Edition by Molecular Probes, Inc. (EugeneOreg.); or Haugland (2001) Handbook of Fluorescent Probes and ResearchChemicals Eigth Edition by Molecular Probes, Inc. (Eugene Oreg.)(Available on CD ROM).

Amplification-Based Detection Methods

PCR, RT-PCR and LCR are in particularly broad use as amplification andamplification-detection methods for amplifying nucleic acids of interest(e.g., those comprising marker loci), facilitating detection of themarkers. Details regarding the use of these and other amplificationmethods can be found in any of a variety of standard texts, including,e.g., Sambrook, Ausubel, Berger and Croy, herein. Many available biologytexts also have extended discussions regarding PCR and relatedamplification methods. One of skill will appreciate that essentially anyRNA can be converted into a double stranded DNA suitable for restrictiondigestion, PCR expansion and sequencing using reverse transcriptase anda polymerase (“Reverse Transcription-PCR, or “RT-PCR”). See also,Ausubel, Sambrook and Berger, above.

Real Time Amplification/Detection Methods

In one aspect, real time PCR or LCR is performed on the amplificationmixtures described herein, e.g., using molecular beacons or TaqMan™probes. A molecular beacon (MB) is an oligonucleotide or PNA which,under appropriate hybridization conditions, self-hybridizes to form astem and loop structure. The MB has a label and a quencher at thetermini of the oligonucleotide or PNA; thus, under conditions thatpermit intra-molecular hybridization, the label is typically quenched(or at least altered in its fluorescence) by the quencher. Underconditions where the MB does not display intra-molecular hybridization(e.g., when bound to a target nucleic acid, e.g., to a region of anamplicon during amplification), the MB label is unquenched. Detailsregarding standard methods of making and using MBs are well establishedin the literature and MBs are available from a number of commercialreagent sources. See also, e.g., Leone et al. (1995) “Molecular beaconprobes combined with amplification by NASBA enable homogenous real-timedetection of RNA.” Nucleic Acids Res. 26:2150-2155; Tyagi and Kramer(1996) “Molecular beacons: probes that fluoresce upon hybridization”Nature Biotechnology 14:303-308; Blok and Kramer (1997) “Amplifiablehybridization probes containing a molecular switch” Mol Cell Probes11:187-194; Hsuih et al. (1997) “Novel, ligation-dependent PCR assay fordetection of hepatitis C in serum” J Clin Microbiol 34:501-507;Kostrikis et al. (1998) “Molecular beacons: spectral genotyping of humanalleles” Science 279:1228-1229; Sokol et al. (1998) “Real time detectionof DNA:RNA hybridization in living cells” Proc. Natl. Acad. Sci. U.S.A.95:11538-11543; Tyagi et al. (1998) “Multicolor molecular beacons forallele discrimination” Nature Biotechnology 16:49-53; Bonnet et al.(1999) “Thermodynamic basis of the chemical specificity of structuredDNA probes” Proc. Natl. Acad. Sci. U.S.A. 96:6171-6176; Fang et al.(1999) “Designing a novel molecular beacon for surface-immobilized DNAhybridization studies” J. Am. Chem. Soc. 121:2921-2922; Marras et al.(1999) “Multiplex detection of single-nucleotide variation usingmolecular beacons” Genet. Anal. Biomol. Eng. 14:151-156; and Vet et al.(1999) “Multiplex detection of four pathogenic retroviruses usingmolecular beacons” Proc. Natl. Acad. Sci. U.S.A. 96:6394-6399.Additional details regarding MB construction and use is found in thepatent literature, e.g., U.S. Pat. No. 5,925,517 (Jul. 20, 1999) toTyagi et al. entitled “Detectably labeled dual conformationoligonucleotide probes, assays and kits;” U.S. Pat. No. 6,150,097 toTyagi et al (Nov. 21, 2000) entitled “Nucleic acid detection probeshaving non-FRET fluorescence quenching and kits and assays includingsuch probes” and U.S. Pat. No. 6,037,130 to Tyagi et al (Mar. 14, 2000),entitled “Wavelength-shifting probes and primers and their use in assaysand kits.”

PCR detection and quantification using dual-labeled fluorogenicoligonucleotide probes, commonly referred to as “TaqMan™” probes, canalso be performed according to the present invention. These probes arecomposed of short (e.g., 20-25 base) oligodeoxynucleotides that arelabeled with two different fluorescent dyes. On the 5′ terminus of eachprobe is a reporter dye, and on the 3′ terminus of each probe aquenching dye is found. The oligonucleotide probe sequence iscomplementary to an internal target sequence present in a PCR amplicon.When the probe is intact, energy transfer occurs between the twofluorophores and emission from the reporter is quenched by the quencherby FRET. During the extension phase of PCR, the probe is cleaved by 5′nuclease activity of the polymerase used in the reaction, therebyreleasing the reporter from the oligonucleotide-quencher and producingan increase in reporter emission intensity. Accordingly, TaqMan™ probesare oligonucleotides that have a label and a quencher, where the labelis released during amplification by the exonuclease action of thepolymerase used in amplification. This provides a real time measure ofamplification during synthesis. A variety of TaqMan™ reagents arecommercially available, e.g., from Applied Biosystems (DivisionHeadquarters in Foster City, Calif.) as well as from a variety ofspecialty vendors such as Biosearch Technologies (e.g., black holequencher probes).

Additional Details Regarding Amplified Variable Sequences, SSR, AFLPASH, SNPs and Isozyme Markers

Amplified variable sequences refer to amplified sequences of the plantgenome which exhibit high nucleic acid residue variability betweenmembers of the same species. All organisms have variable genomicsequences and each organism (with the exception of a clone) has adifferent set of variable sequences. Once identified, the presence ofspecific variable sequence can be used to predict phenotypic traits.Preferably, DNA from the plant serves as a template for amplificationwith primers that flank a variable sequence of DNA. The variablesequence is amplified and then sequenced.

Alternatively, self-sustained sequence replication can be used toidentify genetic markers. Self-sustained sequence replication refers toa method of nucleic acid amplification using target nucleic acidsequences which are replicated exponentially in vitro undersubstantially isothermal conditions by using three enzymatic activitiesinvolved in retroviral replication: (1) reverse transcriptase, (2) RnaseH, and (3) a DNA-dependent RNA polymerase (Guatelli et al. (1990) ProcNatl Acad Sci USA 87:1874). By mimicking the retroviral strategy of RNAreplication by means of cDNA intermediates, this reaction accumulatescDNA and RNA copies of the original target.

Amplified fragment length polymophisms (AFLP) can also be used asgenetic markers (Vos et al. (1995) Nucl Acids Res 23:4407). The phrase“amplified fragment length polymorphism” refers to selected restrictionfragments which are amplified before or after cleavage by a restrictionendonuclease. The amplification step allows easier detection of specificrestriction fragments. AFLP allows the detection large numbers ofpolymorphic markers and has been used for genetic mapping of plants(Becker et al. (1995) Mol Gen Genet 249:65; and Meksem et al. (1995) MolGen Genet 249:74).

Allele-specific hybridization (ASH) can be used to identify the geneticmarkers of the invention. ASH technology is based on the stableannealing of a short, single-stranded, oligonucleotide probe to acompletely complementary single-strand target nucleic acid. Detection isvia an isotopic or non-isotopic label attached to the probe.

For each polymorphism, two or more different ASH probes are designed tohave identical DNA sequences except at the polymorphic nucleotides. Eachprobe will have exact homology with one allele sequence so that therange of probes can distinguish all the known alternative allelesequences. Each probe is hybridized to the target DNA. With appropriateprobe design and hybridization conditions, a single-base mismatchbetween the probe and target DNA will prevent hybridization. In thismanner, only one of the alternative probes will hybridize to a targetsample that is homozygous or homogenous for an allele. Samples that areheterozygous or heterogeneous for two alleles will hybridize to both oftwo alternative probes.

ASH markers are used as dominant markers where the presence or absenceof only one allele is determined from hybridization or lack ofhybridization by only one probe. The alternative allele may be inferredfrom the lack of hybridization. ASH probe and target molecules areoptionally RNA or DNA; the target molecules are any length ofnucleotides beyond the sequence that is complementary to the probe; theprobe is designed to hybridize with either strand of a DNA target; theprobe ranges in size to conform to variously stringent hybridizationconditions, etc.

PCR allows the target sequence for ASH to be amplified from lowconcentrations of nucleic acid in relatively small volumes. Otherwise,the target sequence from genomic DNA is digested with a restrictionendonuclease and size separated by gel electrophoresis. Hybridizationstypically occur with the target sequence bound to the surface of amembrane or, as described in U.S. Pat. No. 5,468,613, the ASH probesequence may be bound to a membrane.

In one embodiment, ASH data are typically obtained by amplifying nucleicacid fragments (amplicons) from genomic DNA using PCR, transferring theamplicon target DNA to a membrane in a dot-blot format, hybridizing alabeled oligonucleotide probe to the amplicon target, and observing thehybridization dots by autoradiography.

Single nucleotide polymorphisms (SNP) are markers that consist of ashared sequence differentiated on the basis of a single nucleotide.Typically, this distinction is detected by differential migrationpatterns of an amplicon comprising the SNP on e.g., an acrylamide gel.However, alternative modes of detection, such as hybridization, e.g.,ASH, or RFLP analysis are also appropriate.

Isozyme markers can be employed as genetic markers, e.g., to trackmarkers other than the tolerance markers herein, or to track isozymemarkers linked to the markers herein. Isozymes are multiple forms ofenzymes that differ from one another in their amino acid, and thereforetheir nucleic acid sequences. Some isozymes are multimeric enzymescontaining slightly different subunits. Other isozymes are eithermultimeric or monomeric but have been cleaved from the proenzyme atdifferent sites in the amino acid sequence. Isozymes can becharacterized and analyzed at the protein level, or alternatively,isozymes which differ at the nucleic acid level can be determined. Insuch cases any of the nucleic acid based methods described herein can beused to analyze isozyme markers.

Additional Details Regarding Nucleic Acid Amplification

As noted, nucleic acid amplification techniques such as PCR and LCR arewell known in the art and can be applied to the present invention toamplify and/or detect nucleic acids of interest, such as nucleic acidscomprising marker loci. Examples of techniques sufficient to directpersons of skill through such in vitro methods, including the polymerasechain reaction (PCR), the ligase chain reaction (LCR), Qβ-replicaseamplification and other RNA polymerase mediated techniques (e.g.,NASBA), are found in the references noted above, e.g., Innis, Sambrook,Ausubel, Berger and Croy. Additional details are found in Mullis et al.(1987) U.S. Pat. No. 4,683,202; Arnheim & Levinson (Oct. 1, 1990) C&EN36-47; The Journal Of NIH Research (1991) 3, 81-94; (Kwoh et al. (1989)Proc. Natl. Acad. Sci. USA 86, 1173; Guatelli et al. (1990) Proc. Natl.Acad. Sci. USA 87, 1874; Lomell et al. (1989) J. Clin. Chem 35, 1826;Landegren et al., (1988) Science 241, 1077-1080; Van Brunt (1990)Biotechnology 8, 291-294; Wu and Wallace, (1989) Gene 4, 560; Barringeret al. (1990) Gene 89, 117, and Sooknanan and Malek (1995) Biotechnology13: 563-564. Improved methods of amplifying large nucleic acids by PCR,which is useful in the context of positional cloning, are furthersummarized in Cheng et al. (1994) Nature 369: 684, and the referencestherein, in which PCR amplicons of up to 40 kb are generated.

Detection of Markers for Positional Cloning

In some embodiments, a nucleic acid probe is used to detect a nucleicacid that comprises a marker sequence. Such probes can be used, forexample, in positional cloning to isolate nucleotide sequences linked tothe marker nucleotide sequence. It is not intended that the nucleic acidprobes of the invention be limited to any particular size. In someembodiments, nucleic acid probe is at least 20 nucleotides in length, oralternatively, at least 50 nucleotides in length, or alternatively, atleast 100 nucleotides in length, or alternatively, at least 200nucleotides in length.

A hybridized probe is detected using, autoradiography, fluorography orother similar detection techniques depending on the label to bedetected. Examples of specific hybridization protocols are widelyavailable in the art, see, e.g., Berger, Sambrook, and Ausubel, allherein.

Probe/Primer Synthesis Methods

In general, synthetic methods for making oligonucleotides, includingprobes, primers, molecular beacons, PNAs, LNAs (locked nucleic acids),etc., are well known. For example, oligonucleotides can be synthesizedchemically according to the solid phase phosphoramidite triester methoddescribed by Beaucage and Caruthers (1981), Tetrahedron Letts.,22(20):1859-1862, e.g., using a commercially available automatedsynthesizer, e.g., as described in Needham-VanDevanter et al. (1984)Nucleic Acids Res., 12:6159-6168. Oligonucleotides, including modifiedoligonucleotides can also be ordered from a variety of commercialsources known to persons of skill. There are many commercial providersof oligo synthesis services, and thus this is a broadly accessibletechnology. Any nucleic acid can be custom ordered from any of a varietyof commercial sources, such as The Midland Certified Reagent Company,The Great American Gene Company, ExpressGen Inc., Operon TechnologiesInc. (Alameda, Calif.) and many others. Similarly, PNAs can be customordered from any of a variety of sources, such as PeptidoGenic, HTIBio-Products, Inc., BMA Biomedicals Ltd (U.K.), Bio-Synthesis, Inc., andmany others.

In Silico Marker Detection

In alternative embodiments, in silico methods can be used to detect themarker loci of interest. For example, the sequence of a nucleic acidcomprising the marker locus of interest can be stored in a computer. Thedesired marker locus sequence or its homolog can be identified using anappropriate nucleic acid search algorithm as provided by, for example,in such readily available programs as BLAST, or even simple wordprocessors.

Amplification Primers for Marker Detection

In some preferred embodiments, the molecular markers of the inventionare detected using a suitable PCR-based detection method, where the sizeor sequence of the PCR amplicon is indicative of the absence or presenceof the marker (e.g., a particular marker allele). In these types ofmethods, PCR primers are hybridized to the conserved regions flankingthe polymorphic marker region. As used in the art, PCR primers used toamplify a molecular marker are sometimes termed “PCR markers” or simply“markers.”

It will be appreciated that, although many specific examples of primersare provided herein (see, FIG. 2), suitable primers to be used with theinvention can be designed using any suitable method. It is not intendedthat the invention be limited to any particular primer or primer pair.For example, primers can be designed using any suitable softwareprogram, such as LASERGENE®.

In some embodiments, the primers of the invention are radiolabelled, orlabeled by any suitable means (e.g., using a non-radioactive fluorescenttag), to allow for rapid visualization of the different size ampliconsfollowing an amplification reaction without any additional labeling stepor visualization step. In some embodiments, the primers are not labeled,and the amplicons are visualized following their size resolution, e.g.,following agarose gel electrophoresis. In some embodiments, ethidiumbromide staining of the PCR amplicons following size resolution allowsvisualization of the different size amplicons.

It is not intended that the primers of the invention be limited togenerating an amplicon of any particular size. For example, the primersused to amplify the marker loci and alleles herein are not limited toamplifying the entire region of the relevant locus. The primers cangenerate an amplicon of any suitable length that is longer or shorterthan those given in the allele definitions in FIG. 3. In someembodiments, marker amplification produces an amplicon at least 20nucleotides in length, or alternatively, at least 50 nucleotides inlength, or alternatively, at least 100 nucleotides in length, oralternatively, at least 200 nucleotides in length. Marker alleles inaddition to those recited in FIG. 4 also find use with the presentinvention.

Marker Assisted Selection and Breeding Plants

A primary motivation for development of molecular markers in cropspecies is the potential for increased efficiency in plant breedingthrough marker assisted selection (MAS). Genetic markers are used toidentify plants that contain a desired genotype at one or more loci, andthat are expected to transfer the desired genotype, along with a desiredphenotype to their progeny. Genetic markers can be used to identifyplants that contain a desired genotype at one locus, or at severalunlinked or linked loci (e.g., a haplotype), and that would be expectedto transfer the desired genotype, along with a desired phenotype totheir progeny. The present invention provides the means to identifyplants, particularly soybean plants, that are tolerant, exhibit improvedtolerance or are susceptible to Fusarium solani infection by identifyingplants having a specified allele at one of those loci, e.g., SATT300,SATT591, SATT155, SATT266, SATT282, SATT412, SATT506, SATT355, SATT452,S60602-TB, SATT142, SATT181, SATT448, S60375-TB, SATT513, SATT549,SATT660, SATT339 and SATT255.

Similarly, by identifying plants lacking the desired marker locus,susceptible or less tolerant plants can be identified, and, e.g.,eliminated from subsequent crosses. Similarly, these marker loci can beintrogressed into any desired genomic background, germplasm, plant,line, variety, etc., as part of an overall MAS breeding program designedto enhance soybean yield.

The invention also provides chromosome QTL intervals that find equal usein MAS to select plants that demonstrate Fusarium solani tolerance orimproved tolerance. Similarly, the QTL intervals can also be used tocounter-select plants that are susceptible or have reduced tolerance toFusarium solani infection. Any marker that maps within the QTL interval(including the termini of the intervals) finds use with the invention.These intervals are defined by the following pairs of markers that arethe interval termini:

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N),

In general, MAS uses polymorphic markers that have been identified ashaving a significant likelihood of co-segregation with a tolerancetrait. Such markers are presumed to map near a gene or genes that givethe plant its tolerance phenotype, and are considered indicators for thedesired trait, and are termed QTL markers. Plants are tested for thepresence of a desired allele in the QTL marker. The most preferredmarkers (or marker alleles) are those that have the strongestassociation with the tolerance trait.

Linkage analysis is used to determine which polymorphic marker alleledemonstrates a statistical likelihood of co-segregation with thetolerance phenotype (thus, a “tolerance marker allele”). Followingidentification of a marker allele for co-segregation with the tolerancephenotype, it is possible to use this marker for rapid, accuratescreening of plant lines for the tolerance allele without the need togrow the plants through their life cycle and await phenotypicevaluations, and furthermore, permits genetic selection for theparticular tolerance allele even when the molecular identity of theactual tolerance QTL is unknown. Tissue samples can be taken, forexample, from the first leaf of the plant and screened with theappropriate molecular marker, and it is rapidly determined which progenywill advance. Linked markers also remove the impact of environmentalfactors that can often influence phenotypic expression.

A polymorphic QTL marker locus can be used to select plants that containthe marker allele (or alleles) that correlate with the desired tolerancephenotype, typically called marker-assisted selection (MAS). In brief, anucleic acid corresponding to the marker nucleic acid allele is detectedin a biological sample from a plant to be selected. This detection cantake the form of hybridization of a probe nucleic acid to a markerallele or amplicon thereof, e.g., using allele-specific hybridization,Southern analysis, northern analysis, in situ hybridization,hybridization of primers followed by PCR amplification of a region ofthe marker, or the like. A variety of procedures for detecting markersare described herein, e.g., in the section entitled “TECHNIQUES FORMARKER DETECTION.” After the presence (or absence) of a particularmarker allele in the biological sample is verified, the plant isselected, e.g., used to make progeny plants by selective breeding.

Soybean plant breeders desire combinations of tolerance loci with genesfor high yield and other desirable traits to develop improved soybeanvarieties. Screening large numbers of samples by non-molecular methods(e.g., trait evaluation in soybean plants) can be expensive, timeconsuming, and unreliable. Use of the polymorphic markers describedherein, when genetically-linked to tolerance loci, provide an effectivemethod for selecting resistant varieties in breeding programs. Forexample, one advantage of marker-assisted selection over fieldevaluations for tolerance resistance is that MAS can be done at any timeof year, regardless of the growing season. Moreover, environmentaleffects are largely irrelevant to marker-assisted selection.

When a population is segregating for multiple loci affecting one ormultiple traits, e.g., multiple loci involved in tolerance, or multipleloci each involved in tolerance or resistance to different diseases, theefficiency of MAS compared to phenotypic screening becomes even greater,because all of the loci can be evaluated in the lab together from asingle sample of DNA. In the present instance, the SATT300, SATT591,SATT155, SATT266, SATT282, SATT412, SATT506, SATT355, SATT452,S60602-TB, SATT142, SATT181, SATT448, S60375-TB, SATT513, SATT549,SATT660, SATT339 and SATT255 markers, as well as any of the chromosomeintervals

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N),        can be assayed simultaneously or sequentially from a single        sample or from a plurality of parallel samples.

Another use of MAS in plant breeding is to assist the recovery of therecurrent parent genotype by backcross breeding. Backcross breeding isthe process of crossing a progeny back to one of its parents or parentlines. Backcrossing is usually done for the purpose of introgressing oneor a few loci from a donor parent (e.g., a parent comprising desirabletolerance marker loci) into an otherwise desirable genetic backgroundfrom the recurrent parent (e.g., an otherwise high yielding soybeanline). The more cycles of backcrossing that are done, the greater thegenetic contribution of the recurrent parent to the resultingintrogressed variety. This is often necessary, because tolerant plantsmay be otherwise undesirable, e.g., due to low yield, low fecundity, orthe like. In contrast, strains which are the result of intensivebreeding programs may have excellent yield, fecundity or the like,merely being deficient in one desired trait such as tolerance toFusarium solani infection.

The presence and/or absence of a particular genetic marker or allele,e.g., SATT300, SATT591, SATT155, SATT266, SATT282, SATT412, SATT506,SATT355, SATT452, S60602-TB, SATT142, SATT181, SATT448, S60375-TB,SATT513, SATT549, SATT660, SATT339 and SATT255 markers, as well as anyof the chromosome intervals

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N),        in the genome of a plant is made by any method noted herein. If        the nucleic acids from the plant are positive for a desired        genetic marker allele, the plant can be self fertilized to        create a true breeding line with the same genotype, or it can be        crossed with a plant with the same marker or with other desired        characteristics to create a sexually crossed hybrid generation.

Introgression of Favorable Alleles—Efficient Backcrossing of ToleranceMarkers into Elite Lines

One application of MAS, in the context of the present invention is touse the tolerance or improved tolerance markers to increase theefficiency of an introgression or backcrossing effort aimed atintroducing a tolerance QTL into a desired (typically high yielding)background. In marker assisted backcrossing of specific markers (andassociated QTL) from a donor source, e.g., to an elite or exotic geneticbackground, one selects among backcross progeny for the donor trait andthen uses repeated backcrossing to the elite or exotic line toreconstitute as much of the elite/exotic background's genome aspossible.

Thus, the markers and methods of the present invention can be utilizedto guide marker assisted selection or breeding of soybean varieties withthe desired complement (set) of allelic forms of chromosome segmentsassociated with superior agronomic performance (tolerance, along withany other available markers for yield, disease resistance, etc.). Any ofthe disclosed marker alleles can be introduced into a soybean line viaintrogression, by traditional breeding (or introduced viatransformation, or both) to yield a soybean plant with superioragronomic performance. The number of alleles associated with tolerancethat can be introduced or be present in a soybean plant of the presentinvention ranges from 1 to the number of alleles disclosed herein, eachinteger of which is incorporated herein as if explicitly recited.

The present invention also extends to a method of making a progenysoybean plant and these progeny soybean plants, per se. The methodcomprises crossing a first parent soybean plant with a second soybeanplant and growing the female soybean plant under plant growth conditionsto yield soybean plant progeny. Methods of crossing and growing soybeanplants are well within the ability of those of ordinary skill in theart. Such soybean plant progeny can be assayed for alleles associatedwith tolerance and, thereby, the desired progeny selected. Such progenyplants or seed can be sold commercially for soybean production, used forfood, processed to obtain a desired constituent of the soybean, orfurther utilized in subsequent rounds of breeding. At least one of thefirst or second soybean plants is a soybean plant of the presentinvention in that it comprises at least one of the allelic forms of themarkers of the present invention, such that the progeny are capable ofinheriting the allele.

Often, a method of the present invention is applied to at least onerelated soybean plant such as from progenitor or descendant lines in thesubject soybean plants pedigree such that inheritance of the desiredtolerance allele can be traced. The number of generations separating thesoybean plants being subject to the methods of the present inventionwill generally be from 1 to 20, commonly 1 to 5, and typically 1, 2, or3 generations of separation, and quite often a direct descendant orparent of the soybean plant will be subject to the method (i.e., onegeneration of separation).

Introgression of Favorable Alleles—Incorporation of “Exotic” Germplasmwhile Maintaining Breeding Progress

Genetic diversity is important for long term genetic gain in anybreeding program. With limited diversity, genetic gain will eventuallyplateau when all of the favorable alleles have been fixed within theelite population. One objective is to incorporate diversity into anelite pool without losing the genetic gain that has already been madeand with the minimum possible investment. MAS provide an indication ofwhich genomic regions and which favorable alleles from the originalancestors have been selected for and conserved over time, facilitatingefforts to incorporate favorable variation from exotic germplasm sources(parents that are unrelated to the elite gene pool) in the hopes offinding favorable alleles that do not currently exist in the elite genepool.

For example, the markers of the present invention can be used for MAS incrosses involving elite×exotic soybean lines by subjecting thesegregating progeny to MAS to maintain major yield alleles, along withthe tolerance marker alleles herein.

Positional Cloning

The molecular marker loci and alleles of the present invention, e.g.,SATT300, SATT591, SATT155, SATT266, SATT282, SATT412, SATT506, SATT355,SATT452, S60602-TB, SATT142, SATT181, SATT448, S60375-TB, SATT513,SATT549, SATT660, SATT339 and SATT255 markers, as well as any of thechromosome intervals

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N),        can be used, as indicated previously, to identify a tolerance        QTL, which can be cloned by well established procedures, e.g.,        as described in detail in Ausubel, Berger and Sambrook, herein.

These tolerance clones are first identified by their genetic linkage tomarkers of the present invention. Isolation of a nucleic acid ofinterest is achieved by any number of methods as discussed in detail insuch references as Ausubel, Berger and Sambrook, herein, and Clark, Ed.(1997) Plant Molecular Biology: A Laboratory Manual Springer-Verlag,Berlin.

For example, “positional gene cloning” uses the proximity of a tolerancemarker to physically define an isolated chromosomal fragment containinga tolerance QTL gene. The isolated chromosomal fragment can be producedby such well known methods as digesting chromosomal DNA with one or morerestriction enzymes, or by amplifying a chromosomal region in apolymerase chain reaction (PCR), or any suitable alternativeamplification reaction. The digested or amplified fragment is typicallyligated into a vector suitable for replication, and, e.g., expression,of the inserted fragment. Markers that are adjacent to an open readingframe (ORF) associated with a phenotypic trait can hybridize to a DNAclone (e.g., a clone from a genomic DNA library), thereby identifying aclone on which an ORF (or a fragment of an ORF) is located. If themarker is more distant, a fragment containing the open reading frame isidentified by successive rounds of screening and isolation of cloneswhich together comprise a contiguous sequence of DNA, a process termed“chromosome walking”, resulting in a “contig” or “contig map.” Protocolssufficient to guide one of skill through the isolation of clonesassociated with linked markers are found in, e.g. Berger, Sambrook andAusubel, all herein.

Generation of Transgenic Cells and Plants

The present invention also relates to host cells and organisms which aretransformed with nucleic acids corresponding to tolerance QTL identifiedaccording to the invention. For example, such nucleic acids includechromosome intervals (e.g., genomic fragments), ORFs and/or cDNAs thatencode a tolerance or improved tolerance trait. Additionally, theinvention provides for the production of polypeptides that providetolerance or improved tolerance by recombinant techniques.

General texts which describe molecular biological techniques for thecloning and manipulation of nucleic acids and production of encodedpolypeptides include Berger and Kimmel, Guide to Molecular CloningTechniques, Methods in Enzymology volume 152 Academic Press, Inc., SanDiego, Calif. (Berger); Sambrook et al., Molecular Cloning—A LaboratoryManual (3rd Ed.), Vol. 1-3, Cold Spring Harbor Laboratory, Cold SpringHarbor, N.Y., 2001 (“Sambrook”) and Current Protocols in MolecularBiology, F. M. Ausubel et al., eds., Current Protocols, a joint venturebetween Greene Publishing Associates, Inc. and John Wiley & Sons, Inc.,(supplemented through 2004 or later) (“Ausubel”)). These texts describemutagenesis, the use of vectors, promoters and many other relevanttopics related to, e.g., the generation of clones that comprise nucleicacids of interest, e.g., marker loci, marker probes, QTL that segregatewith marker loci, etc.

Host cells are genetically engineered (e.g., transduced, transfected,transformed, etc.) with the vectors of this invention (e.g., vectors,such as expression vectors which comprise an ORF derived from or relatedto a tolerance QTL) which can be, for example, a cloning vector, ashuttle vector or an expression vector. Such vectors are, for example,in the form of a plasmid, a phagemid, an agrobacterium, a virus, a nakedpolynucleotide (linear or circular), or a conjugated polynucleotide.Vectors can be introduced into bacteria, especially for the purpose ofpropagation and expansion. The vectors are also introduced into planttissues, cultured plant cells or plant protoplasts by a variety ofstandard methods known in the art, including but not limited toelectroporation (From et al. (1985) Proc. Natl. Acad. Sci. USA 82;5824), infection by viral vectors such as cauliflower mosaic virus(CaMV) (Hohn et al. (1982) Molecular Biology of Plant Tumors (AcademicPress, New York, pp. 549-560; Howell U.S. Pat. No. 4,407,956), highvelocity ballistic penetration by small particles with the nucleic acideither within the matrix of small beads or particles, or on the surface(Klein et al. (1987) Nature 327; 70), use of pollen as vector (WO85/01856), or use of Agrobacterium tumefaciens or A. rhizogenes carryinga T-DNA plasmid in which DNA fragments are cloned. The T-DNA plasmid istransmitted to plant cells upon infection by Agrobacterium tumefaciens,and a portion is stably integrated into the plant genome (Horsch et al.(1984) Science 233; 496; Fraley et al. (1983) Proc. Natl. Acad. Sci. USA80; 4803). Additional details regarding nucleic acid introductionmethods are found in Sambrook, Berger and Ausubel, infra. The method ofintroducing a nucleic acid of the present invention into a host cell isnot critical to the instant invention, and it is not intended that theinvention be limited to any particular method for introducing exogenousgenetic material into a host cell. Thus, any suitable method, e.g.,including but not limited to the methods provided herein, which providesfor effective introduction of a nucleic acid into a cell or protoplastcan be employed and finds use with the invention.

The engineered host cells can be cultured in conventional nutrient mediamodified as appropriate for such activities as, for example, activatingpromoters or selecting transformants. These cells can optionally becultured into transgenic plants. In addition to Sambrook, Berger andAusubel, all infra, Plant regeneration from cultured protoplasts isdescribed in Evans et al. (1983) “Protoplast Isolation and Culture,”Handbook of Plant Cell Cultures 1, 124-176 (MacMillan Publishing Co.,New York; Davey (1983) “Recent Developments in the Culture andRegeneration of Plant Protoplasts,” Protoplasts, pp. 12-29, (Birkhauser,Basel); Dale (1983) “Protoplast Culture and Plant Regeneration ofCereals and Other Recalcitrant Crops,” Protoplasts pp. 31-41,(Birkhauser, Basel); Binding (1985) “Regeneration of Plants,” PlantProtoplasts, pp. 21-73, (CRC Press, Boca Raton, Fla.). Additionaldetails regarding plant cell culture and regeneration include Payne etal. (1992) Plant Cell and Tissue Culture in Liquid Systems John Wiley &Sons, Inc. New York, N.Y.; Gamborg and Phillips (eds) (1995) Plant Cell,Tissue and Organ Culture; Fundamental Methods Springer Lab Manual,Springer-Verlag (Berlin Heidelberg New York) and Plant Molecular Biology(1993) R. R. D. Croy, Ed. Bios Scientific Publishers, Oxford, U.K. ISBN0 12 198370 6. Cell culture media in general are also set forth in Atlasand Parks (eds) The Handbook of Microbiological Media (1993) CRC Press,Boca Raton, Fla. Additional information for cell culture is found inavailable commercial literature such as the Life Science Research CellCulture Catalogue (1998) from Sigma-Aldrich, Inc (St Louis, Mo.)(“Sigma-LSRCCC”) and, e.g., the Plant Culture Catalogue and supplement(e.g., 1997 or later) also from Sigma-Aldrich, Inc (St Louis, Mo.)(“Sigma-PCCS”).

The present invention also relates to the production of transgenicorganisms, which may be bacteria, yeast, fungi, animals or plants,transduced with the nucleic acids of the invention (e.g., nucleic acidscomprising the marker loci and/or QTL noted herein). A thoroughdiscussion of techniques relevant to bacteria, unicellular eukaryotesand cell culture is found in references enumerated herein and arebriefly outlined as follows. Several well-known methods of introducingtarget nucleic acids into bacterial cells are available, any of whichmay be used in the present invention. These include: fusion of therecipient cells with bacterial protoplasts containing the DNA, treatmentof the cells with liposomes containing the DNA, electroporation,projectile bombardment (biolistics), carbon fiber delivery, andinfection with viral vectors (discussed further, below), etc. Bacterialcells can be used to amplify the number of plasmids containing DNAconstructs of this invention. The bacteria are grown to log phase andthe plasmids within the bacteria can be isolated by a variety of methodsknown in the art (see, for instance, Sambrook). In addition, a plethoraof kits are commercially available for the purification of plasmids frombacteria. For their proper use, follow the manufacturer's instructions(see, for example, EasyPrep™, FlexiPrep™, both from Pharmacia Biotech;StrataClean™, from Stratagene; and, QIAprep™ from Qiagen). The isolatedand purified plasmids are then further manipulated to produce otherplasmids, used to transfect plant cells or incorporated intoAgrobacterium tumefaciens related vectors to infect plants. Typicalvectors contain transcription and translation terminators, transcriptionand translation initiation sequences, and promoters useful forregulation of the expression of the particular target nucleic acid. Thevectors optionally comprise generic expression cassettes containing atleast one independent terminator sequence, sequences permittingreplication of the cassette in eukaryotes, or prokaryotes, or both,(e.g., shuttle vectors) and selection markers for both prokaryotic andeukaryotic systems. Vectors are suitable for replication and integrationin prokaryotes, eukaryotes, or preferably both. See, Giliman & Smith(1979) Gene 8:81; Roberts et al. (1987) Nature 328:731; Schneider et al.(1995) Protein Expr. Purif. 6435:10; Ausubel, Sambrook, Berger (allinfra). A catalogue of Bacteria and Bacteriophages useful for cloning isprovided, e.g., by the ATCC, e.g., The ATCC Catalogue of Bacteria andBacteriophage (1992) Gherna et al. (eds) published by the ATCC.Additional basic procedures for sequencing, cloning and other aspects ofmolecular biology and underlying theoretical considerations are alsofound in Watson et al. (1992) Recombinant DNA, Second Edition,Scientific American Books, NY. In addition, essentially any nucleic acid(and virtually any labeled nucleic acid, whether standard ornon-standard) can be custom or standard ordered from any of a variety ofcommercial sources, such as the Midland Certified Reagent Company(Midland, Tex.), The Great American Gene Company (Ramona, Calif.),ExpressGen Inc. (Chicago, Ill.), Operon Technologies Inc. (Alameda,Calif.) and many others.

Introducing Nucleic Acids into Plants

Embodiments of the present invention pertain to the production oftransgenic plants comprising the cloned nucleic acids, e.g., isolatedORFs and cDNAs encoding tolerance genes. Techniques for transformingplant cells with nucleic acids are widely available and can be readilyadapted to the invention. In addition to Berger, Ausubel and Sambrook,all infra, useful general references for plant cell cloning, culture andregeneration include Jones (ed) (1995) Plant Gene Transfer andExpression Protocols—Methods in Molecular Biology, Volume 49 HumanaPress Towata N.J.; Payne et al. (1992) Plant Cell and Tissue Culture inLiquid Systems John Wiley & Sons, Inc. New York, N.Y. (Payne); andGamborg and Phillips (eds) (1995) Plant Cell, Tissue and Organ Culture;Fundamental Methods Springer Lab Manual, Springer-Verlag (BerlinHeidelberg New York) (Gamborg). A variety of cell culture media aredescribed in Atlas and Parks (eds) The Handbook of Microbiological Media(1993) CRC Press, Boca Raton, Fla. (Atlas). Additional information forplant cell culture is found in available commercial literature such asthe Life Science Research Cell Culture Catalogue (1998) fromSigma-Aldrich, Inc (St Louis, Mo.) (Sigma-LSRCCC) and, e.g., the PlantCulture Catalogue and supplement (1997) also from Sigma-Aldrich, Inc (StLouis, Mo.) (Sigma-PCCS). Additional details regarding plant cellculture are found in Croy, (ed.) (1993) Plant Molecular Biology, BiosScientific Publishers, Oxford, U.K.

The nucleic acid constructs of the invention, e.g., plasmids, cosmids,artificial chromosomes, DNA and RNA polynucleotides, are introduced intoplant cells, either in culture or in the organs of a plant by a varietyof conventional techniques. Where the sequence is expressed, thesequence is optionally combined with transcriptional and translationalinitiation regulatory sequences which direct the transcription ortranslation of the sequence from the exogenous DNA in the intendedtissues of the transformed plant.

Isolated nucleic acid acids of the present invention can be introducedinto plants according to any of a variety of techniques known in theart. Techniques for transforming a wide variety of higher plant speciesare also well known and described in widely available technical,scientific, and patent literature. See, for example, Weising et al.(1988) Ann. Rev. Genet. 22:421-477.

The DNA constructs of the invention, for example plasmids, phagemids,cosmids, phage, naked or variously conjugated-DNA polynucleotides,(e.g., polylysine-conjugated DNA, peptide-conjugated DNA,liposome-conjugated DNA, etc.), or artificial chromosomes, can beintroduced directly into the genomic DNA of the plant cell usingtechniques such as electroporation and microinjection of plant cellprotoplasts, or the DNA constructs can be introduced directly to plantcells using ballistic methods, such as DNA particle bombardment.

Microinjection techniques for injecting plant, e.g., cells, embryos,callus and protoplasts, are known in the art and well described in thescientific and patent literature. For example, a number of methods aredescribed in Jones (ed) (1995) Plant Gene Transfer and ExpressionProtocols—Methods in Molecular Biology. Volume 49 Humana Press, Towata,N.J., as well as in the other references noted herein and available inthe literature.

For example, the introduction of DNA constructs using polyethyleneglycol precipitation is described in Paszkowski, et al., EMBO J. 3:2717(1984). Electroporation techniques are described in Fromm, et al., Proc.Natl. Acad. Sci. USA 82:5824 (1985). Ballistic transformation techniquesare described in Klein, et al., Nature 327:70-73 (1987). Additionaldetails are found in Jones (1995) and Gamborg and Phillips (1995),supra, and in U.S. Pat. No. 5,990,387.

Alternatively, and in some cases preferably, Agrobacterium mediatedtransformation is employed to generate transgenic plants.Agrobacterium-mediated transformation techniques, including disarmingand use of binary vectors, are also well described in the scientificliterature. See, for example, Horsch, et al. (1984) Science 233:496; andFraley et al. (1984) Proc. Nat'l. Acad. Sci. USA 80:4803 and recentlyreviewed in Hansen and Chilton (1998) Current Topics in Microbiology240:22 and Das (1998) Subcellular Biochemistry 29: Plant MicrobeInteractions, pp 343-363.

DNA constructs are optionally combined with suitable T-DNA flankingregions and introduced into a conventional Agrobacterium tumefacienshost vector. The virulence functions of the Agrobacterium tumefacienshost will direct the insertion of the construct and adjacent marker intothe plant cell DNA when the cell is infected by the bacteria. See, U.S.Pat. No. 5,591,616. Although Agrobacterium is useful primarily indicots, certain monocots can be transformed by Agrobacterium. Forinstance, Agrobacterium transformation of maize is described in U.S.Pat. No. 5,550,318.

Other methods of transfection or transformation include (1)Agrobacterium rhizogenes-mediated transformation (see, e.g.,Lichtenstein and Fuller (1987) In: Genetic Engineering, vol. 6, P W JRigby, Ed., London, Academic Press; and Lichtenstein; C. P., and Draper(1985) In: DNA Cloning, Vol. II, D. M. Glover, Ed., Oxford, IRI Press;WO 88/02405, published Apr. 7, 1988, describes the use of A. rhizogenesstrain A4 and its Ri plasmid along with A. tumefaciens vectors pARC8 orpARC16 (2) liposome-mediated DNA uptake (see, e.g., Freeman et al.(1984) Plant Cell Physiol. 25:1353), (3) the vortexing method (see,e.g., Kindle (1990) Proc. Natl. Acad. Sci., (USA) 87:1228.

DNA can also be introduced into plants by direct DNA transfer intopollen as described by Zhou et al. (1983) Methods in Enzymology,101:433; D. Hess (1987) Intern Rev. Cytol. 107:367; Luo et al. (1988)Plant Mol. Biol. Reporter 6:165. Expression of polypeptide coding genescan be obtained by injection of the DNA into reproductive organs of aplant as described by Pena et al. (1987) Nature 325:274. DNA can also beinjected directly into the cells of immature embryos and the desiccatedembryos rehydrated as described by Neuhaus et al. (1987) Theor. Appl.Genet. 75:30; and Benbrook et al. (1986) in Proceedings Bio ExpoButterworth, Stoneham, Mass., pp. 27-54. A variety of plant viruses thatcan be employed as vectors are known in the art and include cauliflowermosaic virus (CaMV), geminivirus, brome mosaic virus, and tobacco mosaicvirus.

Generation/Regeneration of Transgenic Plants

Transformed plant cells which are derived by any of the abovetransformation techniques can be cultured to regenerate a whole plantthat possesses the transformed genotype and thus the desired phenotype.Such regeneration techniques rely on manipulation of certainphytohormones in a tissue culture growth medium, typically relying on abiocide and/or herbicide marker which has been introduced together withthe desired nucleotide sequences. Plant regeneration from culturedprotoplasts is described in Payne et al. (1992) Plant Cell and TissueCulture in Liquid Systems John Wiley & Sons, Inc. New York, N.Y.;Gamborg and Phillips (eds) (1995) Plant Cell, Tissue and Organ Culture;Fundamental Methods Springer Lab Manual, Springer-Verlag (BerlinHeidelberg New York); Evans et al. (1983) Protoplasts Isolation andCulture, Handbook of Plant Cell Culture pp. 124-176, MacmillianPublishing Company, New York; and Binding (1985) Regeneration of Plants,Plant Protoplasts pp. 21-73, CRC Press, Boca Raton. Regeneration canalso be obtained from plant callus, explants, somatic embryos (Dandekaret al. (1989) J. Tissue Cult. Meth. 12:145; McGranahan, et al. (1990)Plant Cell Rep. 8:512) organs, or parts thereof. Such regenerationtechniques are described generally in Klee et al. (1987), Ann. Rev. ofPlant Phys. 38:467-486. Additional details are found in Payne (1992) andJones (1995), both supra, and Weissbach and Weissbach, eds. (1988)Methods for Plant Molecular Biology Academic Press, Inc., San Diego,Calif. This regeneration and growth process includes the steps ofselection of transformant cells and shoots, rooting the transformantshoots and growth of the plantlets in soil. These methods are adapted tothe invention to produce transgenic plants bearing QTLs and other genesisolated according to the methods of the invention.

In addition, the regeneration of plants containing the polynucleotide ofthe present invention and introduced by Agrobacterium into cells of leafexplants can be achieved as described by Horsch et al. (1985) Science227:1229-1231. In this procedure, transformants are grown in thepresence of a selection agent and in a medium that induces theregeneration of shoots in the plant species being transformed asdescribed by Fraley et al. (1983) Proc. Natl. Acad. Sci. (U.S.A.)80:4803. This procedure typically produces shoots within two to fourweeks and these transformant shoots are then transferred to anappropriate root-inducing medium containing the selective agent and anantibiotic to prevent bacterial growth. Transgenic plants of the presentinvention may be fertile or sterile.

It is not intended that plant transformation and expression ofpolypeptides that provide disease resistance, as provided by the presentinvention, be limited to soybean species. Indeed, it is contemplatedthat the polypeptides that provide disease tolerance in soybean can alsoprovide disease resistance when transformed and expressed in otheragronomically and horticulturally important species. Such speciesinclude primarily dicots, e.g., of the families: Leguminosae (includingpea, beans, lentil, peanut, yam bean, cowpeas, velvet beans, soybean,clover, alfalfa, lupine, vetch, lotus, sweet clover, wisteria, andsweetpea); and, Compositae (the largest family of vascular plants,including at least 1,000 genera, including important commercial cropssuch as sunflower).

Additionally, preferred targets for modification with the nucleic acidsof the invention, as well as those specified above, plants from thegenera: Allium, Apium, Arachis, Brassica, Capsicum, Cicer, Cucumis,Curcubita, Daucus, Fagopyrum, Glycine, Helianthus, Lactuca, Lens,Lycopersicon, Medicago, Pisum, Phaseolus, Solanum, Trifolium, Vigna, andmany others.

Common crop plants which are targets of the present invention includesoybean, sunflower, canola, peas, beans, lentils, peanuts, yam beans,cowpeas, velvet beans, clover, alfalfa, lupine, vetch, sweet clover,sweetpea, field pea, fava bean, broccoli, brussel sprouts, cabbage,cauliflower, kale, kohlrabi, celery, lettuce, carrot, onion, pepper,potato, eggplant and tomato.

In construction of recombinant expression cassettes of the invention,which include, for example, helper plasmids comprising virulencefunctions, and plasmids or viruses comprising exogenous DNA sequencessuch as structural genes, a plant promoter fragment is optionallyemployed which directs expression of a nucleic acid in any or alltissues of a regenerated plant. Examples of constitutive promotersinclude the cauliflower mosaic virus (CaMV) 35S transcription initiationregion, the 1′- or 2′-promoter derived from T-DNA of Agrobacteriumtumefaciens, and other transcription initiation regions from variousplant genes known to those of skill. Alternatively, the plant promotermay direct expression of the polynucleotide of the invention in aspecific tissue (tissue-specific promoters) or may be otherwise undermore precise environmental control (inducible promoters). Examples oftissue-specific promoters under developmental control include promotersthat initiate transcription only in certain tissues, such as fruit,seeds or flowers.

Any of a number of promoters which direct transcription in plant cellscan be suitable. The promoter can be either constitutive or inducible.In addition to the promoters noted above, promoters of bacterial originthat operate in plants include the octopine synthase promoter, thenopaline synthase promoter and other promoters derived from native Tiplasmids. See, Herrara-Estrella et al. (1983), Nature, 303:209. Viralpromoters include the 35S and 19S RNA promoters of cauliflower mosaicvirus. See, Odell et al. (1985) Nature, 313:810. Other plant promotersinclude Kunitz trypsin inhibitor promoter (KTI), SCP1, SUP, UCD3, theribulose-1,3-bisphosphate carboxylase small subunit promoter and thephaseolin promoter. The promoter sequence from the E8 gene and othergenes may also be used. The isolation and sequence of the E8 promoter isdescribed in detail in Deikman and Fischer (1988) EMBO J. 7:3315. Manyother promoters are in current use and can be coupled to an exogenousDNA sequence to direct expression of the nucleic acid.

If expression of a polypeptide from a cDNA is desired, a polyadenylationregion at the 3′-end of the coding region is typically included. Thepolyadenylation region can be derived from the natural gene, from avariety of other plant genes, or from, e.g., T-DNA.

The vector comprising the sequences (e.g., promoters or coding regions)from genes encoding expression products and transgenes of the inventionwill typically include a nucleic acid subsequence, a marker gene whichconfers a selectable, or alternatively, a screenable, phenotype on plantcells. For example, the marker can encode biocide tolerance,particularly antibiotic tolerance, such as tolerance to kanamycin, G418,bleomycin, hygromycin, or herbicide tolerance, such as tolerance tochlorosluforon, or phosphinothricin (the active ingredient in theherbicides bialaphos or Basta). See, e.g., Padgette et al. (1996) In:Herbicide-Resistant Crops (Duke, ed.), pp 53-84, CRC Lewis Publishers,Boca Raton (“Padgette, 1996”). For example, crop selectivity to specificherbicides can be conferred by engineering genes into crops that encodeappropriate herbicide metabolizing enzymes from other organisms, such asmicrobes. See, Vasil (1996) In: Herbicide-Resistant Crops (Duke, ed.),pp 85-91, CRC Lewis Publishers, Boca Raton) (“Vasil”, 1996).

One of skill will recognize that after the recombinant expressioncassette is stably incorporated in transgenic plants and confirmed to beoperable, it can be introduced into other plants by sexual crossing. Anyof a number of standard breeding techniques can be used, depending uponthe species to be crossed. In vegetatively propagated crops, maturetransgenic plants can be propagated by the taking of cuttings or bytissue culture techniques to produce multiple identical plants.Selection of desirable transgenics is made and new varieties areobtained and propagated vegetatively for commercial use. In seedpropagated crops, mature transgenic plants can be self crossed toproduce a homozygous inbred plant. The inbred plant produces seedcontaining the newly introduced heterologous nucleic acid. These seedscan be grown to produce plants that would produce the selectedphenotype. Parts obtained from the regenerated plant, such as flowers,seeds, leaves, branches, fruit, and the like are included in theinvention, provided that these parts comprise cells comprising theisolated nucleic acid of the present invention. Progeny and variants,and mutants of the regenerated plants are also included within the scopeof the invention, provided that these parts comprise the introducednucleic acid sequences.

Transgenic or introgressed plants expressing a polynucleotide of thepresent invention can be screened for transmission of the nucleic acidof the present invention by, for example, standard nucleic aciddetection methods or by immunoblot protocols. Expression at the RNAlevel can be determined to identify and quantitate expression-positiveplants. Standard techniques for RNA analysis can be employed and includeRT-PCR amplification assays using oligonucleotide primers designed toamplify only heterologous or introgressed RNA templates and solutionhybridization assays using marker or linked QTL specific probes. Plantscan also be analyzed for protein expression, e.g., by Western immunoblotanalysis using antibodies that recognize the encoded polypeptides. Inaddition, in situ hybridization and immunocytochemistry according tostandard protocols can be done using heterologous nucleic acid specificpolynucleotide probes and antibodies, respectively, to localize sites ofexpression within transgenic tissue. Generally, a number of transgeniclines are usually screened for the incorporated nucleic acid to identifyand select plants with the most appropriate expression profiles.

A preferred embodiment of the invention is a transgenic plant that ishomozygous for the added heterologous nucleic acid; e.g., a transgenicplant that contains two added nucleic acid sequence copies, e.g., a geneat the same locus on each chromosome of a homologous chromosome pair. Ahomozygous transgenic plant can be obtained by sexually mating(self-fertilizing) a heterozygous transgenic plant that contains asingle added heterologous nucleic acid, germinating some of the seedproduced and analyzing the resulting plants produced for alteredexpression of a polynucleotide of the present invention relative to acontrol plant (e.g., a native, non-transgenic plant). Back-crossing to aparental plant and out-crossing with a non-transgenic plant can be usedto introgress the heterologous nucleic acid into a selected background(e.g., an elite or exotic soybean line).

Methods for Identifying Fusarium solani-Tolerant Soybean Plants

Experienced plant breeders can recognize tolerant soybean plants in thefield, and can select the tolerant individuals or populations forbreeding purposes or for propagation. In this context, the plant breederrecognizes “tolerant” and “non-tolerant,” or “susceptible” soybeanplants.

Such plant breeding practitioners will appreciate that plant toleranceis a phenotypic spectrum consisting of extremes in tolerance,susceptibility and a continuum of intermediate tolerance phenotypes.Tolerance also varies due to environmental effects and the severity ofpathogen infection. Evaluation of phenotypes using reproducible assaysand tolerance scoring methods are of value to scientists who seek toidentify genetic loci that impart tolerance, conduct marker assistedselection for tolerant population, and for introgression techniques tobreed a tolerance trait into an elite soybean line, for example.

Various methods are known in the art for determining (and measuring) thetolerance of a soybean plant to Fusarium solani infection. For example,Njiti et al. (2003) “Roundup Ready Soybean: Glyphosate Effects onFusarium solani Root Colonization and Sudden Death Syndrome,” Agron. J.95(5):1140-1145 describe a tolerance measurement scale of 1-9, with 1=nodisease and 9=total necrosis caused by Fusarium solani. In one preferredscale which is also in use, this numbering scale is reversed, i.e., 9=Nodisease; 8=very slight symptoms including virus like crinkling and smallchlorotic spots; 7=larger chlorotic spots on less than 20% of theleaves; 6=browning and coalescing of spots; 5=extensive browning andcurling of top leaves; 4=leaves dropping, lower leaves browning andcurling; 3=top stem dying, lower leaves dropping; 2=middle stem dying;1=plants are totally necrotic (dried up plant skeletons). It will beappreciated that all such scales are relative and that numbering andprecise correlation to any scale can be performed at the discretion ofthe practitioner.

Typically, individual field tests are monitored for SDS symptoms duringthe middle to late vegetative stages, but such symptoms typically appearin the early reproductive stage (during flowering and early pod set).Data collection is usually done in 3 or 4 successive scorings about 7days apart. Scorings continue until worsening symptoms can no longer bequantified or until the symptoms are confounded by other factors such asother diseases, insect pressure, severe weather, or advancing maturity.

In general, while there is a certain amount of subjectivity to assigningseverity measurements for disease caused symptoms, assignment to a givenscale as noted above is well within the skill of a practitioner in thefield. Measurements can also be averaged across multiple scorers toreduce variation in field measurements. Furthermore, although protocolsusing artificial inoculation of field nurseries with Fusarium solani cancertainly be used in assessing tolerance, it is also typical fortolerance ratings to be based on actual field observations of fortuitousnatural disease incidence, with the information corresponding to diseaseincidence for a cultivar being averaged over many locations and,typically, several years of crop growing.

If there is no disease present, the rating system above is inapplicable,because everything in an uninfected field scores as tolerant. However,if SDS does occur in a specific field location, all of the lines at thatlocation can be scored as noted above. These scores can accumulate overlocations and years to show disease tolerance for given cultivars. Thus,older lines can have more years of observation than newer ones etc.However, relative measurements can easily be made using the scoringsystem noted above. Furthermore, the tolerance ratings can be updatedand refined each year based on the previous year's observations in thefield. Based on this, SDS scores for a cultivar are relativemeasurements of tolerance.

The experiments described herein (see, Example 1) score soybeantolerance to Fusarium solani infection using the following scale: 9=nodisease symptoms; 8=very slight symptoms including virus like crinklingand small chlorotic spots; 7=larger chlorotic spots on less than 20% ofthe leaves; 6=browning and coalescing of spots; 5=extensive browning andcurling of top leaves; 4=leaves dropping, lower leaves browning andcurling; 3=top stem dying, lower leaves dropping; 2=middle stem dying;1=plants are totally necrotic (dried up plant skeletons).

In assessing linkage of markers to tolerance, either quantitative orqualitative approaches can be used. For example, an actual averagerating for each line that is a single number (for each line) from 1 to 9can be assessed for linkage. This approach is quantitative and uses thescores from lines that have both marker data and SDS scores. In analternative approach, an “intergroup” comparison of tolerant versussusceptible lines is used. In this approach, those soybean lines thatare considered to be representative of either the tolerant ofsusceptible classes are used for assessing linkage. A list of tolerantlines is constructed, e.g., having average rating of 6 to 9 on the abovescale (when averaged over years and locations). The susceptible linesare those with an average rating of 1 to 4 over years and locations.Only lines that can be reliably placed in the 2 groups are used. Once aline is included in the group, it is treated as an equal in thatgroup—i.e. the actual quantitative ratings are not used.

Lines are scored in field screening based both disease severity anddisease incidence compiled into one score. Known susceptible andtolerant lines are placed in the field to verify the intensity andseverity of the disease. Plots are scored on a 1 to 9 scale where 1=allplants showing foliar leaf symptoms with severe scorch while 9 equals noplants with foliar symptoms. This data is analyzed over years to developa final characterization for variety.

The method described above can also easily be adapted to test whetherplant tolerance is race-specific or non-race specific. For example, acandidate soybean strain can be tested for tolerance to a variety ofpreviously identified Fusarium races, where the virulent races have beenshown to infect formerly resistant soybean plants. In this case, aplurality of Fusarium races are used to inoculate the plant cultivarsassessed in the assay. If the soybean plants are tolerant to all theFusarium races tested, or to a subset of the races tested, the soybeanstrain can be considered to have non-race specific tolerance, orpartially non-race specific tolerance.

Automated Detection/Correlation Systems of the Invention

In some embodiments, the present invention includes an automated systemfor detecting markers of the invention and/or correlating the markerswith a desired phenotype (e.g., tolerance). Thus, a typical system caninclude a set of marker probes or primers configured to detect at leastone favorable allele of one or more marker locus associated withtolerance or improved tolerance to Fusarium solani infection. Theseprobes or primers are configured to detect the marker alleles noted inthe tables and examples herein, e.g., using any available alleledetection format, e.g., solid or liquid phase array based detection,microfluidic-based sample detection, etc.

For example, in one embodiment, the marker locus is SATT300, SATT591,SATT155, SATT266, SATT282, SATT412, SATT506, SATT355, SATT452,S60602-TB, SATT142, SATT181, SATT448, S60375-TB, SATT513, SATT549,SATT660, SATT339 or SATT255, or any combination thereof, as well as anyof the chromosome intervals:

-   -   (i) SATT300 and SATT155 (LG-A1);    -   (ii) SATT282 and SATT506 (LG-D1b); and    -   (iii) SATT549 and SATT255 (LG-N),        and the probe set is configured to detect the locus.

The typical system includes a detector that is configured to detect oneor more signal outputs from the set of marker probes or primers, oramplicon thereof, thereby identifying the presence or absence of theallele. A wide variety of signal detection apparatus are available,including photo multiplier tubes, spectrophotometers, CCD arrays, arraysand array scanners, scanning detectors, phototubes and photodiodes,microscope stations, galvo-scanns, microfluidic nucleic acidamplification detection appliances and the like. The preciseconfiguration of the detector will depend, in part, on the type of labelused to detect the marker allele, as well as the instrumentation that ismost conveniently obtained for the user. Detectors that detectfluorescence, phosphorescence, radioactivity, pH, charge, absorbance,luminescence, temperature, magnetism or the like can be used. Typicaldetector embodiments include light (e.g., fluorescence) detectors orradioactivity detectors. For example, detection of a light emission(e.g., a fluorescence emission) or other probe label is indicative ofthe presence or absence of a marker allele. Fluorescent detection isespecially preferred and is generally used for detection of amplifiednucleic acids (however, upstream and/or downstream operations can alsobe performed on amplicons, which can involve other detection methods).In general, the detector detects one or more label (e.g., light)emission from a probe label, which is indicative of the presence orabsence of a marker allele.

The detector(s) optionally monitors one or a plurality of signals froman amplification reaction. For example, the detector can monitor opticalsignals which correspond to “real time” amplification assay results.

System instructions that correlate the presence or absence of thefavorable allele with the predicted tolerance are also a feature of theinvention. For example, the instructions can include at least onelook-up table that includes a correlation between the presence orabsence of the favorable alleles and the predicted tolerance or improvedtolerance. The precise form of the instructions can vary depending onthe components of the system, e.g., they can be present as systemsoftware in one or more integrated unit of the system (e.g., amicroprocessor, computer or computer readable medium), or can be presentin one or more units (e.g., computers or computer readable media)operably coupled to the detector. As noted, in one typical embodiment,the system instructions include at least one look-up table that includesa correlation between the presence or absence of the favorable allelesand predicted tolerance or improved tolerance. The instructions alsotypically include instructions providing a user interface with thesystem, e.g., to permit a user to view results of a sample analysis andto input parameters into the system.

The system typically includes components for storing or transmittingcomputer readable data representing or designating the alleles detectedby the methods of the present invention, e.g., in an automated system.The computer readable media can include cache, main, and storage memoryand/or other electronic data storage components (hard drives, floppydrives, storage drives, etc.) for storage of computer code. Datarepresenting alleles detected by the method of the present invention canalso be electronically, optically, magnetically o transmitted in acomputer data signal embodied in a transmission medium over a networksuch as an intranet or internet or combinations thereof. The system canalso or alternatively transmit data via wireless, IR, or other availabletransmission alternatives.

During operation, the system typically comprises a sample that is to beanalyzed, such as a plant tissue, or material isolated from the tissuesuch as genomic DNA, amplified genomic DNA, cDNA, amplified cDNA, RNA,amplified RNA, or the like.

The phrase “allele detection/correlation system” in the context of thisinvention refers to a system in which data entering a computercorresponds to physical objects or processes external to the computer,e.g., a marker allele, and a process that, within a computer, causes aphysical transformation of the input signals to different outputsignals. In other words, the input data, e.g., amplification of aparticular marker allele is transformed to output data, e.g., theidentification of the allelic form of a chromosome segment. The processwithin the computer is a set of instructions, or “program,” by whichpositive amplification or hybridization signals are recognized by theintegrated system and attributed to individual samples as a genotype.Additional programs correlate the identity of individual samples withphenotypic values or marker alleles, e.g., statistical methods. Inaddition there are numerous e.g., C/C++ programs for computing, Delphiand/or Java programs for GUI interfaces, and productivity tools (e.g.,Microsoft Excel and/or SigmaPlot) for charting or creating look uptables of relevant allele-trait correlations. Other useful softwaretools in the context of the integrated systems of the invention includestatistical packages such as SAS, Genstat, Matlab, Mathematica, andS-Plus and genetic modeling packages such as QU-GENE. Furthermore,additional programming languages such as visual basic are also suitablyemployed in the integrated systems of the invention.

For example, tolerance marker allele values assigned to a population ofprogeny descending from crosses between elite lines are recorded in acomputer readable medium, thereby establishing a database correspondingtolerance alleles with unique identifiers for members of the populationof progeny. Any file or folder, whether custom-made or commerciallyavailable (e.g., from Oracle or Sybase) suitable for recording data in acomputer readable medium is acceptable as a database in the context ofthe present invention. Data regarding genotype for one or more molecularmarkers, e.g., ASH, SSR, RFLP, RAPD, AFLP, SNP, isozyme markers or othermarkers as described herein, are similarly recorded in a computeraccessible database. Optionally, marker data is obtained using anintegrated system that automates one or more aspects of the assay (orassays) used to determine marker(s) genotype. In such a system, inputdata corresponding to genotypes for molecular markers are relayed from adetector, e.g., an array, a scanner, a CCD, or other detection devicedirectly to files in a computer readable medium accessible to thecentral processing unit. A set of system instructions (typicallyembodied in one or more programs) encoding the correlations betweentolerance and the alleles of the invention is then executed by thecomputational device to identify correlations between marker alleles andpredicted trait phenotypes.

Typically, the system also includes a user input device, such as akeyboard, a mouse, a touchscreen, or the like, for, e.g., selectingfiles, retrieving data, reviewing tables of maker information, etc., andan output device (e.g., a monitor, a printer, etc.) for viewing orrecovering the product of the statistical analysis.

Thus, in one aspect, the invention provides an integrated systemcomprising a computer or computer readable medium comprising set offiles and/or a database with at least one data set that corresponds tothe marker alleles herein. The system also includes a user interfaceallowing a user to selectively view one or more of these databases. Inaddition, standard text manipulation software such as word processingsoftware (e.g., Microsoft Word™ or Corel WordPerfect™) and database orspreadsheet software (e.g., spreadsheet software such as MicrosoftExcel™, Corel Quattro Pro™, or database programs such as MicrosoftAccess™ or Paradox™) can be used in conjunction with a user interface(e.g., a GUI in a standard operating system such as a Windows,Macintosh, Unix or Linux system) to manipulate strings of characterscorresponding to the alleles or other features of the database.

The systems optionally include components for sample manipulation, e.g.,incorporating robotic devices. For example, a robotic liquid controlarmature for transferring solutions (e.g., plant cell extracts) from asource to a destination, e.g., from a microtiter plate to an arraysubstrate, is optionally operably linked to the digital computer (or toan additional computer in the integrated system). An input device forentering data to the digital computer to control high throughput liquidtransfer by the robotic liquid control armature and, optionally, tocontrol transfer by the armature to the solid support is commonly afeature of the integrated system. Many such automated robotic fluidhandling systems are commercially available. For example, a variety ofautomated systems are available from Caliper Technologies (Hopkinton,Mass.), which utilize various Zymate systems, which typically include,e.g., robotics and fluid handling modules. Similarly, the common ORCA®robot, which is used in a variety of laboratory systems, e.g., formicrotiter tray manipulation, is also commercially available, e.g., fromBeckman Coulter, Inc. (Fullerton, Calif.). As an alternative toconventional robotics, microfluidic systems for performing fluidhandling and detection are now widely available, e.g., from CaliperTechnologies Corp. (Hopkinton, Mass.) and Agilent technologies (PaloAlto, Calif.).

Systems for molecular marker analysis of the present invention can,thus, include a digital computer with one or more of high-throughputliquid control software, image analysis software for analyzing data frommarker labels, data interpretation software, a robotic liquid controlarmature for transferring solutions from a source to a destinationoperably linked to the digital computer, an input device (e.g., acomputer keyboard) for entering data to the digital computer to controlhigh throughput liquid transfer by the robotic liquid control armatureand, optionally, an image scanner for digitizing label signals fromlabeled probes hybridized, e.g., to markers on a solid support operablylinked to the digital computer. The image scanner interfaces with theimage analysis software to provide a measurement of, e.g., nucleic acidprobe label intensity upon hybridization to an arrayed sample nucleicacid population (e.g., comprising one or more markers), where the probelabel intensity measurement is interpreted by the data interpretationsoftware to show whether, and to what degree, the labeled probehybridizes to a marker nucleic acid (e.g., an amplified marker allele).The data so derived is then correlated with sample identity, todetermine the identity of a plant with a particular genotype(s) forparticular markers or alleles, e.g., to facilitate marker assistedselection of soybean plants with favorable allelic forms of chromosomesegments involved in agronomic performance (e.g., tolerance or improvedtolerance).

Optical images, e.g., hybridization patterns viewed (and, optionally,recorded) by a camera or other recording device (e.g., a photodiode anddata storage device) are optionally further processed in any of theembodiments herein, e.g., by digitizing the image and/or storing andanalyzing the image on a computer. A variety of commercially availableperipheral equipment and software is available for digitizing, storingand analyzing a digitized video or digitized optical image, e.g., usingPC (Intel x86 or pentium chip-compatible DOS™, OS2™ WINDOWS™, WINDOWSNT™ or WINDOWS95™ based machines), MACINTOSH™, LINUX, or UNIX based(e.g., SUN™ work station) computers.

EXAMPLES

The following examples are offered to illustrate, but not to limit, theclaimed invention. It is understood that the examples and embodimentsdescribed herein are for illustrative purposes only, and persons skilledin the art will recognize various reagents or parameters that can bealtered without departing from the spirit of the invention or the scopeof the appended claims.

Example 1 Intergroup Allele Frequency Distribution Analysis

Two independent allele frequency distribution analyses were undertakento identify soybean genetic marker loci associated with tolerance toFusarium solani infection. By identifying such genetic markers, markerassisted selection (MAS) can be used to improve the efficiency ofbreeding for improved tolerance of soybean to Fusarium solani infection.

Soybean Lines and Tolerance Scoring

The plant varieties used in the analysis were from diverse sources,including elite germplasm, commercially released cultivars and otherpublic lines representing a broad range of germplasm. The lines used inthe study had a broad maturity range varying from group 0 to group 6.

Two groups of soybean lines were assembled for each analysis based ontheir phenotypic extremes in tolerance to Fusarium solani infestation,where the plants were sorted into either highly susceptible or highlytolerant varieties. The classifications of tolerant and susceptible werebased solely on observations of fortuitous, naturally occurring fieldsdisplaying disease incidence in greenhouse and field tests over severalyears. The degree of plant tolerance to Fusarium solani infection variedwidely, as measured using a scale from one (highly susceptible) to nine(highly tolerant). Generally, a score of two (2) indicated the mostsusceptible strains, and a score of seven (7) was assigned to the mosttolerant lines. A score of one (1) was generally not used, as soybeanstrains with such extremely high susceptibility were not typicallypropagated. Tolerance scores of eight (8) and nine (9) were reserved fortolerance levels that are very rare and generally not observed inexisting germplasm. If no disease was present in a field, no tolerancescoring was done. However, if a disease did occur in a specific fieldlocation, all of the lines in that location were scored. Scores for teststrains accumulated over multiple locations and multiple years, and anaveraged (e.g., consensus) score was ultimately assigned to each line.

Following scale description was used as a guide in scoring the plantsfor Fusarium solani infection:

Score Phenotypic Description 9 No disease 8 very slight symptomsincluding virus like crinkling and small chlorotic spots 7 largerchlorotic spots on less than 20% of the leaves 6 browning and coalescingof spots 5 extensive browning and curling of top leaves 4 leavesdropping, lower leaves browning and curling 3 top stem dying, lowerleaves dropping 2 middle stem dying 1 plants are totally necrotic (driedup plant skeletons)

Depending on the site where the plant scoring was done, differentsusceptible and tolerant checks were planted to verify disease infectionthroughout the field and gauge severity. The plants were scored inStreator, Ill. At this site, the 93B35 and 93B53 lines were the keysusceptibility checks, and 93M11 and 93B68 were key tolerant checks thatwere of similar RM as the RIL's.

Individual fields showing Fusarium solani infection were monitored fordisease symptoms during the reproductive stages, but the majority ofscoring was typically done in the R4 and R7 stages. Data collection wastypically done in 3 successive scorings about 7 days apart. Scoringscontinued until worsening symptoms can no longer be quantified or untilthe symptoms are confounded by other factors such as other diseases,insect pressure, severe weather, or advancing maturity. Scoring was doneuntil leaf senescence at maturity.

In assessing linkage of markers to tolerance, a qualitative “intergroupallele frequency distribution” comparison approach was used. Using thisapproach, those soybean lines that were considered to be representativeof either the tolerant or susceptible classes were used for assessinglinkage. A list of tolerant lines was constructed, where strains havinga tolerance score of 6 or greater were considered “tolerant.” Similarly,soybean lines with scores of four or less were collectively consideredsusceptible. Only lines that could be reliably placed into the twogroups were used. Once a line is included in the “tolerant” or“susceptible” group, it was treated as an equal in that group, i.e., theactual quantitative ratings was not used.

In the study, 100 soybean lines were identified that were consideredtolerant in the phenotypic spectrum; these plants formed the “TOLERANT”group. Also, 105 soybean lines were identified that were judged to besusceptible to Fusarium solani root rot; these strains formed the“SUSCEPTIBLE” group.

Soybean Genotyping

Each of the tolerant and susceptible lines were genotyped with SSR andSNP markers that span the soybean genome using techniques well known inthe art. The genotyping protocol consisted of collecting young leaftissue from eight individuals from each tolerant and resistant soybeanstrain, pooling (i.e., bulking) the leaf tissue from the eightindividuals, and isolating genomic DNA from the pooled tissue. Thesoybean genomic DNA was extracted by the CTAB method, as described inMaroof et al., (1984) Proc. Natl. Acad. Sci. (USA) 81:8014-8018.

The isolated genomic DNA was then used in PCR reactions usingamplification primers specific for a large number of markers thatcovered all chromosomes in the soybean genome. The length of the PCRamplicon or amplicons from each PCR reaction were characterized. Thelength of the amplicons generated in the PCR reactions were compared toknown allele definitions for the various markers (see, e.g., FIG. 3),and allele designations were assigned. SNP-type markers were genotypedusing an ASH protocol.

Intergroup Allele Frequency Analysis

An “Intergroup Allele Frequency Distribution” analysis was conductedusing GeneFlow™ version 7.0 software. An intergroup allele frequencydistribution analysis provides a method for finding non-randomdistributions of alleles between two phenotypic groups.

During processing, a contingency table of allele frequencies isconstructed and from this a G-statistic and probability are calculated(the G statistic is adjusted by using the William's correction factor).The probability value is adjusted to take into account the fact thatmultiple tests are being done (thus, there is some expected rate offalse positives). The adjusted probability is proportional to theprobability that the observed allele distribution differences betweenthe two classes would occur by chance alone. The lower that probabilityvalue, the greater the likelihood that the Fusarium solani infectionphenotype and the marker will co-segregate. A more complete discussionof the derivation of the probability values can be found in theGeneFlow™ version 7.0 software documentation. See, also, Sokal and Rolf(1981), Biometry: The Principles and Practices of Statistics inBiological Research, 2nd ed., San Francisco, W. H. Freeman and Co.

The underlying logic is that markers with significantly different alleledistributions between the tolerant and susceptible groups (i.e., nonrandom distributions) might be associated with the trait and can be usedto separate them for purposes of marker assisted selection of soybeanlines with previously uncharacterized tolerance or susceptibility toFusarium solani SDS. The present analysis examined one marker locus at atime and determined if the allele distribution within the tolerant groupis significantly different from the allele distribution within thesusceptible group. A statistically different allele distribution is anindication that the marker is linked to a locus that is associated withreaction to Sclerotinia stem rot. In this analysis, unadjustedprobabilities less than one are considered significant (the marker andthe phenotype show linkage disequilibrium), and adjusted probabilitiesless than approximately 0.05 are considered highly significant. Alleleclasses represented by less than 5 observations across both groups werenot included in the statistical analysis. In this analysis, 509 markerloci had enough observations for analysis.

This analysis compares the plants' phenotypic score with the genotypesat the various loci. This type of intergroup analysis neither generatesnor requires any map data. Subsequently, map data (for example, acomposite soybean genetic map) is relevant in that multiple significantmarkers that are also genetically linked can be considered ascollaborating evidence that a given chromosomal region is associatedwith the trait of interest.

Results

FIG. 1 provides a table listing the soybean markers that demonstratedlinkage disequilibrium with the Fusarium solani tolerance/susceptibilityphenotype. Also indicated in that figure are the chromosomes on whichthe markers are located and their approximate map position relative toother known markers, given in cM, with position zero being the first(most distal) marker known at the beginning of the chromosome. These mappositions are not absolute, and represent an estimate of map position.The statistical probabilities that the marker allele and tolerancephenotype are segregating independently are reflected in the adjustedprobability values.

FIG. 2 provides the PCR primer sequences that were used to genotypethese marker loci. FIG. 2 also provides the pigtail sequence used on the5′ end of the right SSR-marker primers and the number of nucleotides inthe repeating element in the SSR. The observed alleles that are known tooccur for these marker loci are provided in the allele dictionary inFIG. 3.

Discussion

There are a number of ways to use the information provided in thisanalysis for the development of improved soybean varieties. Oneapplication is to use the associated markers (or more based on a higherprobability cutoff value) as candidates for mapping QTL in specificpopulations that are segregating for plants having tolerance to Fusariumsolani infection. In this application, one proceeds with conventionalQTL mapping in a segregating population, but focusing on the markersthat are associated with Fusarium solani infection tolerance, instead ofusing markers that span the entire genome. This makes mapping effortsmore cost-effective by dramatically reducing lab resources committed tothe project. For example, instead of screening segregating populationswith a large set of markers that spans the entire genome, one wouldscreen with only those few markers that met some statistical cutoff inthe intergroup allele association study. This will not only reduce thecost of mapping but will also eliminate false leads that willundoubtedly occur with a large set of markers. In any given cross, it islikely that only a small subset of the associated markers will actuallybe correlated with tolerance to Fusarium solani infection. Once the fewrelevant markers are identified in any tolerant parent, future markerassisted selection (MAS) efforts can focus on only those markers thatare important for that source of tolerance. By pre-selecting lines thathave the allele associated with tolerance via MAS, one can eliminate theundesirable susceptible lines and concentrate the expensive fieldtesting resources on lines that have a higher probability of beingtolerant to Fusarium solani infection.

Example 2 Association Mapping Analysis

An association mapping strategy was undertaken to identify soybeangenetic markers associated with tolerance to Fusarium solani infection,which is the causative agent of soybean sudden death syndrome (SDS). Thestudy was completed twice, generating two independent data sets. Byidentifying such genetic markers, marker assisted selection (MAS) can beused to improve the efficiency of breeding for improved tolerance ofsoybean to Fusarium solani infection. Association mapping is known inthe art, and is described in various sources, e.g., Jorde (2000), GenomeRes., 10: 1435-1444; Remington et al. (2001), “Structure of linkagedisequilibrium and phenotype associations in the maize genome,” ProcNatl Acad Sci USA 98:11479-11484; and Weiss and Clark (2002), Trends inGenetics 18:19-24.

Association Mapping

Understanding the extent and patterns of linkage disequilibrium (LD) inthe genome is a prerequisite for developing efficient associationapproaches to identify and map quantitative trait loci (QTL). Linkagedisequilibrium (LD) refers to the non-random association of alleles in acollection of individuals. When LD is observed among alleles at linkedloci, it is measured as LD decay across a specific region of achromosome. The extent of the LD is a reflection of the recombinationalhistory of that region. The average rate of LD decay in a genome canhelp predict the number and density of markers that are required toundertake a genome-wide association study and provides an estimate ofthe resolution that can be expected.

Association or LD mapping aims to identify significantgenotype-phenotype associations. It has been exploited as a powerfultool for fine mapping in outcrossing species such as humans (Corder etal. (1994) “Protective effect of apolipoprotein-E type-2 allele forlate-onset Alzheimer-disease,” Nat Genet 7: 180-184; Hastbacka et al.,(1992) “Linkage disequilibrium mapping in isolated founder populations:diastrophic dysplasia in Finland,” Nat Genet 2:204-211; Kerem et al.,(1989) “Identification of the cystic fibrosis gene: genetic analysis,”Science 245:1073-1080) and maize (Remington et al., (2001) “Structure oflinkage disequilibrium and phenotype associations in the maize genome,”Proc Natl Acad Sci USA 98:11479-11484; Thornsberry et al. (2001) “Dwarf8polymorphisms associate with variation in flowering time,” Nat Genet28:286-289; reviewed by Flint-Garcia et al. (2003) “Structure of linkagedisequilibrium in plants,” Annu Rev Plant Biol., 54:357-374), whererecombination among heterozygotes is frequent and results in a rapiddecay of LD. In inbreeding species where recombination among homozygousgenotypes is not genetically detectable, the extent of LD is greater(i.e., larger blocks of linked markers are inherited together) and thisdramatically lowers the resolution of association mapping (Wall andPritchard (2003) “Haplotype blocks and linkage disequilibrium in thehuman genome,” Nat Rev Genet 4:587-597).

The recombinational and mutational history of a population is a functionof the mating habit, as well as the effective size and age of apopulation. Large population sizes offer enhanced possibilities fordetecting recombination, while older populations are generallyassociated with higher levels of polymorphism, both of which contributeto observably accelerated rates of LD decay. On the other hand, smallereffective population sizes, i.e., those that have experienced a recentgenetic bottleneck, tend to show a slower rate of LD decay, resulting inmore extensive haplotype conservation (Flint-Garcia et al. (2003)“Structure of linkage disequilibrium in plants,” Annu Rev Plant Biol.,54:357-374).

Elite breeding lines provide a valuable starting point for associationanalyses. Association analyses use quantitative phenotypic scores (e.g.,disease tolerance rated from one to nine for each soybean line) in theanalysis (as opposed to looking only at tolerant versus resistant allelefrequency distributions in intergroup allele distribution types ofanalysis). The availability of detailed phenotypic performance datacollected by breeding programs over multiple years and environments fora large number of elite lines provides a valuable dataset for geneticmarker association mapping analyses. This paves the way for a seamlessintegration between research and application and takes advantage ofhistorically accumulated data sets. However, an understanding of therelationship between polymorphism and recombination is useful indeveloping appropriate strategies for efficiently extracting maximuminformation from these resources.

This type of association analysis neither generates nor requires any mapdata, but rather, is independent of map position. This analysis comparesthe plants' phenotypic score with the genotypes at the various loci.Subsequently, any suitable soybean map (for example, a composite map)can optionally be used to help observe distribution of the identifiedQTL markers and/or QTL marker clustering using previously determined maplocations of the markers.

Soybean Lines and Phenotypic Scoring

Soybean lines were phenotypically scored based on their degree oftolerance to Fusarium solani infection (in contrast to simplecategorization of “tolerant” or “susceptible”). The plant varieties usedin the analysis were from diverse sources, including elite germplasm,commercially released cultivars and other public varieties. Thecollections comprised 205 soybean lines, or alternatively, 177 lines inthe two analyses. The lines used in the study had a broad maturity rangevarying from group 0 to group 6, but typically lines at R3 (2 years fromcommercial product) or above were used.

The tolerance scoring was based solely on observations in fortuitous,naturally occurring fields displaying disease incidence inmultienvironmental field tests over several years. The degree of planttolerance to Fusarium solani infestation varied widely, as measuredusing a scale from one (1; highly susceptible) to nine (9; highlytolerant). Generally, a score of two (2) indicated the most susceptiblestrains, and a score of seven (8) was assigned to the most tolerantlines. A score of one (1) was generally not used, as soybean strainswith such extremely high susceptibility were not typically propagated. Atolerance score of nine (9) was reserved for tolerance levels that arevery rare and generally not observed in existing germplasm. Adescription of the scale used as a guide in scoring the plants forFusarium solani infection is provided in EXAMPLE 1. If no disease waspresent in a field, no tolerance scoring was done. However, if diseasedid occur in a specific field location, all of the lines in thatlocation were scored. Tolerance scores for the reference strainsaccumulated over multiple locations and years, and an averaged (e.g.,consensus) score was ultimately assigned to each line. Tolerance scoresfor the 205 variety collection or the 177 variety collection werecollected over a single grow season.

Individual fields showing Fusarium solani infestation were monitored fordisease symptoms during the reproductive stages, but were typicallyscored in the R4 to R7 stages. Data collection was typically done infour scorings about seven days apart. Scorings continued until worseningsymptoms can no longer be quantified or until the symptoms areconfounded by other factors such as other diseases, insect pressure,severe weather, or advancing maturity.

In assessing the linkage of markers to tolerance, a quantitativeapproach was used, where a tolerance score for each soybean line wasassessed and incorporated into the association mapping statisticalanalysis.

Soybean Genotyping

The independent populations of either 205 or 177 soybean lines that werescored for disease tolerance were then genotyped. The 205 memberpopulation was genotyped using 287 SSR and ASH markers. The 177 memberpopulation was genotyped using 374 SSR and ASH markers. These SSR andSNP markers collectively spanned each chromosome in the plant genome.The genotyping protocol consisted of collecting young leaf tissue fromeight individuals from each soybean strain, pooling (i.e., bulking) theleaf tissue from the eight individuals, and isolating genomic DNA fromthe pooled tissue. The soybean genomic DNA was extracted by the CTABmethod, as described in Maroof et al., (1984) Proc. Natl. Acad. Sci.(USA) 81:8014-8018.

The isolated genomic DNA was then used in PCR reactions usingamplification primers specific for a large number of markers thatcovered all chromosomes in the soybean genome. The length of the PCRamplicon or amplicons from each PCR reaction were characterized.SNP-type markers were genotyped using an ASH protocol. The length of theamplicons generated in the PCR reactions were compared to known alleledefinitions for the various markers (see FIG. 3), and alleledesignations for each tested marker were assigned.

Statistical Methods

Monomorphic loci are considered uninformative and thus are eliminatedfrom LD analyses. The monomorphic loci are defined as those whose genediversity

$\left( {{1 - {\sum\limits_{i = 1}^{n}p_{i}}},{\text{where~~}p_{i}\text{~~is~~}i^{th}\mspace{14mu}\text{allele~~frequency~~in~~the~~population~~of~~study}}} \right)$is less than 0.10. Since rare alleles (frequency<0.05) tend to causelarge variances for the estimates of r², they were treated as missingdata and pooled together. Marker screening and partitioning areconducted using PowerMarker software (version 2.72), which was developedby Jack Liu.

The rate of LD decay with genetic distance (cM) was calculated for pairsof markers on the same chromosome and was evaluated using linearregression in which the genetic distances were transformed by takinglog₁₀, as described by McRae et al. (2002). Population structure wasevaluated using Pritchard's model-based method (Pritchard et al. 2000)and the software, STRUCTURE (version 2.0). This version of the programcontrols for linked markers and correlated allelic frequencies (Falushet al. (2003) “Inference of population structure using multilocusgenotype data: linked loci and correlated allele frequencies,” Genetics164: 1567-1587). It detects population structure in structured oradmixed populations. This method is more appropriate than conventionallyused genetic distance-based method, because Structure provides thelikelihood associated with different numbers of sub-populations and theestimated percentage of shared ancestry with each sub-population foreach entry.

Associations of individual SSR markers with tolerance to low-ironconditions were evaluated by logistic regression in TASSEL (TraitAnalysis by aSSociation, Evolution, and Linkage) using the StructuredAssociation analysis mode. TASSEL is provided by Edward Buckler, andinformation about the program can be found on the Buckler Lab web pageat the Institute for Genomic Diversity at Cornell University. See,TASSEL Ver. 1.1.0 (released Jun. 23, 2005). The significance level foreach association was tested using an empirical distribution that wasestablished by running 5,000 permutations. Modifications of establishedprocedures were made to accommodate the nature and characteristics ofsoybean and the soybean data set, especially with regard to thoseaspects that differ from rice.

Results

FIG. 1 provides a table listing the soybean markers that demonstratedlinkage disequilibrium with the Fusarium solani tolerance phenotypeusing the Association Mapping method. Also indicated in that figure arethe chromosomes on which the markers are located and their approximatemap position relative to other known markers, given in cM, with positionzero being the first (most distal) marker known at the beginning of thechromosome. These map positions are not absolute, and represent anestimate of map position. The SNP-type markers were detected by anallele specific hybridization (ASH) method, as known in the art (see,e.g., Coryell et al., (1999) “Allele specific hybridization markers forsoybean,” Theor. Appl. Genet., 98:690-696). FIG. 2 provides the PCRprimer sequences that were used to genotype these marker loci. FIG. 2also provides the pigtail sequence used on the 5′ end of the rightSSR-marker primers and the number of nucleotides in the repeatingelement in the SSR. The alleles that are known to occur for the markerloci are provided in the SSR allele dictionary in FIG. 3.

The statistical probabilities that the marker allele and diseasetolerance phenotype are segregating independently are reflected in theassociation mapping adjusted probability values in FIG. 1, which is aprobability (P) derived from 5000 rounds of permutation analysis betweengenotype and phenotype. The permutations method for probability analysisis known in the art, and described in various sources, for example,Churchill and Doerge (1994), Genetics 138: 963-971; Doerge and Churchill(1996), Genetics 142: 285-294; Lynch and Walsh (1998) in Genetics andanalysis of quantitative traits, published by Sinauer Associates, Inc.Sunderland, Mass. 01375, p. 441-442.

The lower the probability value, the more significant is the associationbetween the marker genotype at that locus and the Fusarium solaniinfection tolerance phenotype. A more complete discussion of thederivation of the probability values can be found in the GeneFlow™version 7.0 software documentation. See, also, Sokal and Rolf (1981),Biometry: The Principles and Practices of Statistics in BiologicalResearch, 2nd ed., San Francisco, W. H. Freeman and Co.

Example 3 QTL Interval Mapping and Single Marker Regression Analysis

A QTL interval mapping and a single marker regression analysis wasundertaken to identify soybean chromosome intervals and genetic markers(respectively) that are associated with tolerance and allow the plant toescape the pathology associated with Fusarium solani infection. QTLmapping and marker regression are widely used methods to identifygenetic loci that co-segregate with a desired phenotype. By identifyingsuch genetic loci, marker assisted selection (MAS) can be used toimprove the efficiency of breeding for improved soybean strains.

Soybean Lines

A mapping population for Fusarium solani tolerance was created from thecross of commercially available Pioneer varieties 93B41 and P9362. Thepopulation consisted of 276 RIL progeny.

Phenotypic Scoring

RIL phenotypic data was collected from non-inoculated, non-irrigated,naturally infested field screening site at a site in Streator, Ill. Thescoring scale as described in EXAMPLE 1 was used. Known checks wereplanted along side the experiments to verify disease pressure anduniformity. Phenotypic scoring of each of the 276 lines of progeny wasbased on one set of phenotypic data collected from the field. Based onthat raw data, a composite score was also assigned for each line.

Soybean Genotyping

Soybean progeny were genotyped using a total of 195 polymorphic markers.Markers included genomic-SSR and EST-SSR markers.

Of the 195 markers that were used to screen the RIL population, 143markers produced usable data. Of those 143 markers, all but 12 weremapped to 19 linkage groups. LG-A1 only contained one marker. No markersmapped to LG-D1a. LG-B2, LG-H, LG-I, LG-M and LG-O had three to fourmarkers each. This map covers about 40% of the soybean genome.

MapManager-QTXb20 (2004) was used for both the marker regressionanalysis and QTL interval mapping. The 1000 permutation tests were usedto establish the threshold for statistical significance in the QTLinterval analysis as measured by the likelihood ratio statistic (LRS).The LRS provides a measure of the linkage between variation in thephenotype and genetic differences at a particular genetic locus. LRSvalues can be converted to LOD scores (logarithm of the odds ratio) bydividing by 4.61. The term “likelihood” of “odds” is used to describethe relative probability of two or more explanations of the sources ofvariation in a trait. The probability of these two differentexplanations (models) can be computed, and most likely model chosen. Ifmodel A is 1000 times more probable than model B, then the ratio of theodds are 1000:1 and the logarithm of the odds ratio is 3.

Both the raw data and the composite score were used in QTL intervalmapping. The LRS threshold for raw data and composite score at P=0.05 is13.2 and 12.9, respectively. A confidence interval was estimated foreach QTL by bootstrap resampling. After completing the interval mapping,the program will create multiple resampled datasets, perform intervalmapping again with each of these sets, and record the position of themaximum LRS. The positions obtained are then plotted as a histogramoverlaying the interval mapping figure.

Results

QTL Interval Mapping

The present study identified various chromosome intervals that correlatewith QTL that associate with tolerance/susceptibility to Fusarium solaniinfection. Two QTL were identified using both raw data and compositescores. These QTL for raw data and composite scores are essentiallysame. One QTL is in the vicinity of the Rhg1 locus on LG-G. There is abroad support interval of this QTL with multiple peaks, indicating thatthere might be multiple QTL in this region. This QTL explains 10% of thetotal variation with a favorable allele from the 93B41 strain.

Another QTL is identified on LG-L roughly between SATT166 and SATT513.This QTL explains 9% of the total variation with the favorable allelefrom strain 9362.

Single Marker Regression

Using single marker regression, there are a number of markers showingassociation with the tolerance phenotype at a confidence level of P=0.05or better, as shown in FIG. 1. These markers include clusterings on LG-Land LG-N. There is a concordance of the QTL interval mapping results andthe single marker regression results for the markers on LG-L.

Discussion/Conclusions:

This present study has identified chromosome intervals and individualmarkers that correlate with Fusarium solani tolerance. Markers that liewithin these intervals are useful for use in MAS, as well as otherpurposes.

While the foregoing invention has been described in some detail forpurposes of clarity and understanding, it will be clear to one skilledin the art from a reading of this disclosure that various changes inform and detail can be made without departing from the true scope of theinvention. For example, all the techniques and apparatus described abovecan be used in various combinations. All publications, patents, patentapplications, and/or other documents cited in this application areincorporated by reference in their entirety for all purposes to the sameextent as if each individual publication, patent, patent application,and/or other document were individually indicated to be incorporated byreference for all purposes.

1. A method of identifying a first soybean plant or germplasm thatdisplays tolerance, or improved tolerance to Fusarium solani infection,the method comprising detecting in the first soybean plant or germplasman allele of a marker locus that is associated with the tolerance or,improved tolerance, wherein the marker locus is located within thechromosomal interval defined by and including the termini SATT166 andSATT513.
 2. The method of claim 1, wherein the marker locus associatedwith tolerance, or improved tolerance is SATT513.
 3. The method of claim1, wherein the germplasm is a soybean line or soybean variety.
 4. Themethod of claim 1, wherein the Fusarium solani is Fusarium solani f. sp.glycines.
 5. The method of claim 1, wherein the tolerance or improvedtolerance is a non-race specific tolerance or a non-race specificimproved tolerance.
 6. The method of claim 1, wherein the detectingcomprises detecting at least one allelic form of a polymorphic simplesequence repeat (SSR) or a single nucleotide polymorphism (SNP).
 7. Themethod of claim 1, wherein the detecting comprises amplifying the markerlocus or a portion of the marker locus to produce an amplified markeramplicon, and detecting the resulting amplified marker amplicon.
 8. Themethod of claim 7, wherein the amplifying comprises: a) admixing anamplification primer or amplification primer pair with a nucleic acidisolated from the first soybean plant or germplasm, wherein theamplification primer or amplification primer pair is complementary orpartially complementary to at least a portion of the marker locus, andis capable of initiating DNA polymerization by a DNA polymerase usingthe soybean nucleic acid as a template; and, b) extending theamplification primer or amplification primer pair in a DNApolymerization reaction comprising a DNA polymerase and a templatenucleic acid to generate at least one amplified marker amplicon.
 9. Themethod of claim 8, wherein the nucleic acid is selected from DNA andRNA.
 10. The method of claim 6, wherein the at least one SNP allele isdetected using allele specific hybridization (ASH) analysis.
 11. Themethod of claim 7, wherein the amplifying comprises employing apolymerase chain reaction (PCR) or ligase chain reaction (LCR) using anucleic acid isolated from the first soybean plant or germplasm as atemplate in the PCR or LCR.
 12. The method of claim 1, wherein theallele is a favorable allele that positively correlates with toleranceor improved tolerance.
 13. The method of claim 1, further comprisingselecting the first soybean plant or germplasm, or selecting a progenyof the first soybean plant or germplasm comprising the at least oneallele of a marker locus that is associated with the tolerance orimproved tolerance to Fusarium solani infection.
 14. The method of claim13, further comprising crossing the selected first soybean plant orgermplasm with a second soybean plant or germplasm.
 15. The method ofclaim 14, wherein the second soybean plant or germplasm comprises anexotic soybean strain or an elite soybean strain.
 16. The method ofclaim 1, wherein the marker locus is determined using a mappingpopulation from a cross between soybean lines 93B41 and P9362.
 17. Themethod of claim 1, wherein the tolerance or improved tolerance isassayed in a population of soybean that is naturally infected with theFusarium solani.